Change all instances of DEVMODE to DEVMODEW since the program is unicode

Fix "C28251 Inconsistent annotation for function" compiler warning by correctly defining WinMain.

LICENSE.txt

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) [year] [fullname]
+Copyright (c) 2025 Mina Brown
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -2,15 +2,15 @@
 
 A utility for switching the resolution of your laptop's display based on the current power state.
 
-Currently a work in progress. Not very useful yet since it doesn't save your preferences. It doesn't even have an icon.
+Currently a work in progress. It works reasonably well for a standard single display configuration, but other scenarios have not been extensively tested, and there are some edge cases that may need to be worked out.
 
-This is a simple C program written using Visual Studio 2022 that has no external dependencies. It should support Windows Vista or higher, but this hasn't been tested yet.
+This is a simple C program written using Visual Studio 2022 that has no external dependencies. It supports Windows Vista or higher.
 
 ## TODO
-- [ ] Save preferences to the Windows registry.
-- [ ] Add a checkbox to preferences for starting at login.
-- [ ] Add an icon.
+- [x] Save preferences to the Windows registry.
+- [x] Add a checkbox to preferences for starting at login.
+- [x] Add an icon.
 - [ ] Add behavior for when multiple displays are connected.
-- [ ] Block program from running when the system has no battery.
-- [ ] Make the default display mode the current one instead of the highest resolution if there are no preferences set.
+- [x] Make the default display mode the current one instead of the highest resolution if there are no preferences set.
 - [ ] Make an actual about dialog.
+- [ ] Support dark mode.

WinPowerDMS/DisplayMode.c

@@ -0,0 +1,109 @@
+#include <stdio.h>
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include "DisplayMode.h"
+
+BOOL DisplayModeEquals(const DISPLAY_MODE* a, const DISPLAY_MODE* b) {
+    return a->width == b->width && a->height == b->height && a->refresh == b->refresh;
+}
+
+// I hate parsing the string here, but the alternative requires extra memory management.
+DISPLAY_MODE GetModeFromCB(HWND hComboBox) {
+    DISPLAY_MODE mode = { 0 };
+    LRESULT selectedIndex = SendMessage(hComboBox, CB_GETCURSEL, 0, 0);
+    if (selectedIndex != CB_ERR) {
+        LRESULT len = SendMessage(hComboBox, CB_GETLBTEXTLEN, selectedIndex, 0);
+        if (len != CB_ERR) {
+            LPWSTR text = HeapAlloc(GetProcessHeap(), 0, len * sizeof(*text));
+            if (text) {
+                SendMessage(hComboBox, CB_GETLBTEXT, selectedIndex, (LPARAM)text);
+                swscanf_s(text, L"%dx%d @ %d Hz", &mode.width, &mode.height, &mode.refresh);
+                HeapFree(GetProcessHeap(), 0, text);
+            }
+        }
+    }
+
+    return mode;
+}
+
+// returns the result of the ChangeDisplaySettings call that this results in.
+LONG ChangeDisplayMode(LPCWSTR displayName, const DISPLAY_MODE* mode, DWORD dwFlags) {
+    DEVMODEW devMode = {
+        .dmSize = sizeof(devMode),
+        .dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY,
+        .dmPelsWidth = mode->width,
+        .dmPelsHeight = mode->height,
+        .dmDisplayFrequency = mode->refresh
+    };
+    if (displayName) wcscpy_s(devMode.dmDeviceName, sizeof(devMode.dmDeviceName) / sizeof(devMode.dmDeviceName[0]), displayName);
+
+    return ChangeDisplaySettings(&devMode, dwFlags);
+}
+
+struct MessageBoxParams {
+    HWND hWnd;
+    LPCWSTR lpText;
+    LPCWSTR lpCaption;
+    UINT uType;
+};
+
+static DWORD WINAPI MessageBoxAsync(LPVOID lpParam) {
+    struct MessageBoxParams* params = lpParam;
+    return MessageBox(params->hWnd, params->lpText, params->lpCaption, params->uType);
+}
+
+struct TestDisplayModeParams {
+    HWND hDlg;
+    WCHAR displayName[32];
+    DISPLAY_MODE mode;
+};
+
+static DWORD WINAPI TestDisplayModeThread(LPVOID lpParam) {
+    struct TestDisplayModeParams* params = lpParam;
+    DEVMODEW originalMode = { .dmSize = sizeof(originalMode) };
+    EnumDisplaySettings(params->displayName, ENUM_CURRENT_SETTINGS, &originalMode);
+    ChangeDisplayMode(params->displayName, &params->mode, CDS_FULLSCREEN);
+
+    // Create the message box about the resolution change
+    WCHAR msgText[96];
+    swprintf_s(msgText, sizeof(msgText) / sizeof(msgText[0]),
+        L"Testing %dx%d @ %d Hz\nThe display mode will reset back in 10 seconds.",
+        params->mode.width, params->mode.height, params->mode.refresh);
+    struct MessageBoxParams mbParams = {
+        .hWnd = params->hDlg,
+        .lpText = msgText,
+        .lpCaption = L"Resolution Test",
+        .uType = MB_OK | MB_ICONINFORMATION
+    };
+    HANDLE mbThread = CreateThread(NULL, 0, MessageBoxAsync, &mbParams, 0, NULL);
+    if (mbThread) {
+        CloseHandle(mbThread);
+        Sleep(10000);
+        ChangeDisplaySettings(&originalMode, 0);
+    }
+    else {
+        MessageBox(params->hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
+    }
+    HeapFree(GetProcessHeap(), 0, params);
+    return 0;
+}
+
+void TestDisplayMode(HWND hDlg, LPCWSTR displayName, DISPLAY_MODE* mode) {
+    struct TestDisplayModeParams* tdmParams = HeapAlloc(GetProcessHeap(), 0, sizeof(*tdmParams));
+    if (tdmParams) {
+        tdmParams->hDlg = hDlg;
+        if (tdmParams->displayName) wcscpy_s(tdmParams->displayName, sizeof(tdmParams->displayName) / sizeof(tdmParams->displayName[0]), displayName);
+        tdmParams->mode = *mode;
+        HANDLE tdmThread = CreateThread(NULL, 0, TestDisplayModeThread, tdmParams, 0, NULL);
+        if (tdmThread) CloseHandle(tdmThread);
+        else {
+            HeapFree(GetProcessHeap(), 0, tdmParams);
+            MessageBox(hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
+        }
+    }
+    else {
+        MessageBox(hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
+    }
+}

WinPowerDMS/DisplayMode.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+typedef struct {
+	DWORD width;
+	DWORD height;
+	DWORD refresh;
+} DISPLAY_MODE;
+
+BOOL DisplayModeEquals(const DISPLAY_MODE* a, const DISPLAY_MODE* b);
+
+DISPLAY_MODE GetModeFromCB(HWND hComboBox);
+
+// returns the result of the ChangeDisplaySettings call that this results in.
+LONG ChangeDisplayMode(LPCWSTR displayName, const DISPLAY_MODE* mode, DWORD dwFlags);
+
+void TestDisplayMode(HWND hDlg, LPCWSTR displayName,  DISPLAY_MODE* mode);

WinPowerDMS/WinPowerDMS.c

@@ -1,9 +1,14 @@
+#define WIN32_LEAN_AND_MEAN
+#define _WIN32_WINNT _WIN32_WINNT_VISTA
+#define NTDDI_VERSION NTDDI_VISTA
+
 #include <stdio.h>
 #include <windows.h>
 #include <shellapi.h>
 #include <commctrl.h>
 
 #include "resource.h"
+#include "DisplayMode.h"
 
 // Link Common Controls v6 for visual styling
 #pragma comment(linker,"\"/manifestdependency:type='win32' \
@@ -14,130 +19,97 @@ processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
 #define TRAY_ICON_ID 1001
 
 typedef struct {
-    int width;
-    int height;
-    int refresh;
-} DISPLAY_MODE;
+    DISPLAY_MODE modeBatt;
+    DISPLAY_MODE modeAC;
+    BOOL runAtStartup;
+} WINPOWERDMS_PREFS;
 
-static DISPLAY_MODE modeBatt = { 0 };
-static DISPLAY_MODE modeAC = { 0 };
+static WINPOWERDMS_PREFS userPrefs = { 0 };
 
-BOOL DisplayModeEquals(const DISPLAY_MODE* a, const DISPLAY_MODE* b) {
-    return a->width == b->width && a->height == b->height && a->refresh == b->refresh;
-}
+// Save user preferences to registry.
+static BOOL SavePrefs(void) {
+    BOOL saved = FALSE;
 
-#define MODE_SELECTED(mode) (!DisplayModeEquals(&mode, &(DISPLAY_MODE) { 0 }))
-
-// I hate parsing the string here, but the alternative requires extra memory management.
-static DISPLAY_MODE GetModeFromCB(HWND hDlg, int nIDDlgItem) {
-    DISPLAY_MODE mode = { 0 };
-    HWND hComboBox = GetDlgItem(hDlg, nIDDlgItem);
-    size_t selectedIndex = SendMessage(hComboBox, CB_GETCURSEL, 0, 0);
-    if (selectedIndex != CB_ERR) {
-        LRESULT len = SendMessage(hComboBox, CB_GETLBTEXTLEN, selectedIndex, 0);
-        if (len != CB_ERR) {
-            LPWSTR text = HeapAlloc(GetProcessHeap(), 0, len * sizeof(*text));
-            if (text) {
-                SendMessage(hComboBox, CB_GETLBTEXT, selectedIndex, (LPARAM) text);
-                swscanf_s(text, L"%dx%d @ %d Hz", &mode.width, &mode.height, &mode.refresh);
-                HeapFree(GetProcessHeap(), 0, text);
-            }
-        }
+    HKEY regKey;
+    if (!RegCreateKeyEx(
+        HKEY_CURRENT_USER, L"SOFTWARE\\WinPowerDMS", 0, NULL,
+        REG_OPTION_NON_VOLATILE, KEY_WRITE, NULL, &regKey, NULL
+    )) {
+        RegSetKeyValue(regKey, L"Battery", L"Width", REG_DWORD, &userPrefs.modeBatt.width, sizeof(userPrefs.modeBatt.width));
+        RegSetKeyValue(regKey, L"Battery", L"Height", REG_DWORD, &userPrefs.modeBatt.height, sizeof(userPrefs.modeBatt.height));
+        RegSetKeyValue(regKey, L"Battery", L"Refresh Rate", REG_DWORD, &userPrefs.modeBatt.refresh, sizeof(userPrefs.modeBatt.refresh));
+        RegSetKeyValue(regKey, L"AC Power", L"Width", REG_DWORD, &userPrefs.modeAC.width, sizeof(userPrefs.modeAC.width));
+        RegSetKeyValue(regKey, L"AC Power", L"Height", REG_DWORD, &userPrefs.modeAC.height, sizeof(userPrefs.modeAC.height));
+        RegSetKeyValue(regKey, L"AC Power", L"Refresh Rate", REG_DWORD, &userPrefs.modeAC.refresh, sizeof(userPrefs.modeAC.refresh));
+        RegCloseKey(regKey);
+        saved = TRUE;
     }
 
-    return mode;
+    // Create the startup entry
+    if (userPrefs.runAtStartup) {
+        WCHAR exePath[MAX_PATH];
+        DWORD exePathLen = GetModuleFileName(NULL, exePath, sizeof(exePath) / sizeof(exePath[0])) + 1;
+        RegSetKeyValue(HKEY_CURRENT_USER, L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run", L"WinPowerDMS", REG_SZ, exePath, exePathLen);
+    }
+    else { // Delete the startup entry
+        RegDeleteKeyValue(HKEY_CURRENT_USER, L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run", L"WinPowerDMS");
+    }
+    return saved;
 }
 
-// returns the result of the ChangeDisplaySettings call that this results in.
-static LONG ChangeDisplayMode(const DISPLAY_MODE* mode, DWORD dwFlags) {
-    DEVMODE devMode = {
-        .dmSize = sizeof(devMode),
-        .dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY,
-        .dmPelsWidth = mode->width,
-        .dmPelsHeight = mode->height,
-        .dmDisplayFrequency = mode->refresh
+// Load user preferences from registry.
+static BOOL LoadPrefs(void) {
+    BOOL loaded = FALSE;
+
+    HKEY regKey;
+    if (!RegOpenKeyEx(HKEY_CURRENT_USER, L"SOFTWARE\\WinPowerDMS", 0, KEY_READ, &regKey)) {
+        DWORD keySize = sizeof(userPrefs.modeBatt.width);
+        RegGetValue(regKey, L"Battery", L"Width", RRF_RT_REG_DWORD, NULL, &userPrefs.modeBatt.width, &keySize);
+        keySize = sizeof(userPrefs.modeBatt.height);
+        RegGetValue(regKey, L"Battery", L"Height", RRF_RT_REG_DWORD, NULL, &userPrefs.modeBatt.height, &keySize);
+        keySize = sizeof(userPrefs.modeBatt.refresh);
+        RegGetValue(regKey, L"Battery", L"Refresh Rate", RRF_RT_REG_DWORD, NULL, &userPrefs.modeBatt.refresh, &keySize);
+        keySize = sizeof(userPrefs.modeAC.width);
+        RegGetValue(regKey, L"AC Power", L"Width", RRF_RT_REG_DWORD, NULL, &userPrefs.modeAC.width, &keySize);
+        keySize = sizeof(userPrefs.modeAC.height);
+        RegGetValue(regKey, L"AC Power", L"Height", RRF_RT_REG_DWORD, NULL, &userPrefs.modeAC.height, &keySize);
+        keySize = sizeof(userPrefs.modeAC.refresh);
+        RegGetValue(regKey, L"AC Power", L"Refresh Rate", RRF_RT_REG_DWORD, NULL, &userPrefs.modeAC.refresh, &keySize);
+        RegCloseKey(regKey);
+        loaded = TRUE;
+    }
+
+    // Figure out if application has a startup entry
+    if (!RegGetValue(HKEY_CURRENT_USER, L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run", L"WinPowerDMS", RRF_RT_ANY, NULL, NULL, NULL))
+        userPrefs.runAtStartup = TRUE;
+    
+    return loaded;
+}
+
+static DISPLAY_MODE GetCurrentDisplayMode(void) {
+    DEVMODEW currentMode = { .dmSize = sizeof(currentMode) };
+    EnumDisplaySettings(NULL, ENUM_CURRENT_SETTINGS, &currentMode);
+    return (DISPLAY_MODE) {
+        .width = currentMode.dmPelsWidth,
+        .height = currentMode.dmPelsHeight,
+        .refresh = currentMode.dmDisplayFrequency
     };
-
-    return ChangeDisplaySettings(&devMode, dwFlags);
 }
 
-struct MessageBoxParams {
-    HWND hWnd;
-    LPCWSTR lpText;
-    LPCWSTR lpCaption;
-    UINT uType;
-};
+static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam) {
+    HWND hComboBatt = GetDlgItem(hDlg, IDC_COMBO_BATT);
+    HWND hComboAC = GetDlgItem(hDlg, IDC_COMBO_AC);
+    HWND hCheckStartup = GetDlgItem(hDlg, IDC_CHECK_STARTUP);
 
-static DWORD WINAPI MessageBoxAsync(LPVOID lpParam) {
-    struct MessageBoxParams* params = lpParam;
-    return MessageBox(params->hWnd, params->lpText, params->lpCaption, params->uType);
-}
-
-struct TestDisplayModeParams {
-    HWND hDlg;
-    DISPLAY_MODE mode;
-};
-
-static DWORD WINAPI TestDisplayModeThread(LPVOID lpParam) {
-    struct TestDisplayModeParams* params = lpParam;
-    DEVMODE originalMode = { .dmSize = sizeof(originalMode) };
-    EnumDisplaySettings(NULL, ENUM_CURRENT_SETTINGS, &originalMode);
-    ChangeDisplayMode(&params->mode, CDS_FULLSCREEN);
-
-    // Create the message box about the resolution change
-    WCHAR msgText[96];
-    swprintf_s(msgText, sizeof(msgText) / sizeof(msgText[0]),
-        L"Testing %dx%d @ %d Hz\nThe display mode will reset back in 10 seconds.",
-        params->mode.width, params->mode.height, params->mode.refresh);
-    struct MessageBoxParams mbParams = {
-        .hWnd = params->hDlg,
-        .lpText = msgText,
-        .lpCaption = L"Resolution Test",
-        .uType = MB_OK | MB_ICONINFORMATION
-    };
-    HANDLE mbThread = CreateThread(NULL, 0, MessageBoxAsync, &mbParams, 0, NULL);
-    if (mbThread) {
-        CloseHandle(mbThread);
-        Sleep(10000);
-        ChangeDisplaySettings(&originalMode, 0);
-    }
-    else {
-        MessageBox(params->hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
-    }
-    HeapFree(GetProcessHeap(), 0, params);
-    return 0;
-}
-
-static void TestDisplayMode(HWND hDlg, DISPLAY_MODE* mode) {
-    struct TestDisplayModeParams* tdmParams = HeapAlloc(GetProcessHeap(), 0, sizeof(*tdmParams));
-    if (tdmParams) {
-        tdmParams->hDlg = hDlg;
-        tdmParams->mode = *mode;
-        HANDLE tdmThread = CreateThread(NULL, 0, TestDisplayModeThread, tdmParams, 0, NULL);
-        if (tdmThread) CloseHandle(tdmThread);
-        else {
-            HeapFree(GetProcessHeap(), 0, tdmParams);
-            MessageBox(hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
-        }
-    }
-    else {
-        MessageBox(hDlg, L"Failed to test resolution.", L"Error", MB_OK | MB_ICONERROR);
-    }
-}
-
-static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
-    switch (message) {
+    switch (uMsg) {
     case WM_INITDIALOG: {
-        HWND hComboBatt = GetDlgItem(hDlg, IDC_COMBO_BATT);
-        HWND hComboAC = GetDlgItem(hDlg, IDC_COMBO_AC);
-
         // devMode object that will be enumerated
-        DEVMODE devMode;
+        DEVMODEW devMode;
         ZeroMemory(&devMode, sizeof(devMode));
         devMode.dmSize = sizeof(devMode);
 
         size_t modeCount = 0;
-        int modeNum = 0;
+        DWORD modeNum = 0;
         DISPLAY_MODE lastMode = { 0 };
         while (EnumDisplaySettings(NULL, modeNum++, &devMode)) {
             DISPLAY_MODE currentMode = {
@@ -154,11 +126,11 @@ static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT message, WPARAM wParam,
 
                 // Add to both combo boxes and check if this is the mode that was set.
                 SendMessage(hComboBatt, CB_ADDSTRING, 0, (LPARAM)resText);
-                if (DisplayModeEquals(&modeBatt, &currentMode))
+                if (DisplayModeEquals(&userPrefs.modeBatt, &currentMode))
                     SendMessage(hComboBatt, CB_SETCURSEL, modeCount, 0);
 
                 SendMessage(hComboAC, CB_ADDSTRING, 0, (LPARAM)resText);
-                if (DisplayModeEquals(&modeAC, &currentMode))
+                if (DisplayModeEquals(&userPrefs.modeAC, &currentMode))
                     SendMessage(hComboAC, CB_SETCURSEL, modeCount, 0);
                 
                 ++modeCount;
@@ -166,9 +138,7 @@ static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT message, WPARAM wParam,
             }
         }
 
-        // select the highest display mode if one hasn't been selected yet
-        if (!MODE_SELECTED(modeBatt)) SendMessage(hComboBatt, CB_SETCURSEL, modeCount - 1, 0);
-        if (!MODE_SELECTED(modeAC)) SendMessage(hComboAC, CB_SETCURSEL, modeCount - 1, 0);
+        SendMessage(hCheckStartup, BM_SETCHECK, userPrefs.runAtStartup ? BST_CHECKED : BST_UNCHECKED, 0);
         return TRUE;
     }
                       
@@ -176,8 +146,10 @@ static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT message, WPARAM wParam,
         switch (LOWORD(wParam)) {
         case IDC_BUTTON_APPLY:
         case IDOK: {
-            modeBatt = GetModeFromCB(hDlg, IDC_COMBO_BATT);
-            modeAC = GetModeFromCB(hDlg, IDC_COMBO_AC);
+            userPrefs.modeBatt = GetModeFromCB(hComboBatt);
+            userPrefs.modeAC = GetModeFromCB(hComboAC);
+            userPrefs.runAtStartup = SendMessage(hCheckStartup, BM_GETCHECK, 0, 0) == BST_CHECKED;
+            SavePrefs();
             if (LOWORD(wParam) == IDC_BUTTON_APPLY) return TRUE;
         }
         case IDCANCEL: {
@@ -185,13 +157,13 @@ static INT_PTR CALLBACK PrefsDialogProc(HWND hDlg, UINT message, WPARAM wParam,
             return TRUE;
         }
         case IDC_BUTTON_TEST_BATT: {
-            DISPLAY_MODE mode = GetModeFromCB(hDlg, IDC_COMBO_BATT);
-            TestDisplayMode(hDlg, &mode);
+            DISPLAY_MODE mode = GetModeFromCB(hComboBatt);
+            TestDisplayMode(hDlg, NULL, &mode);
             return TRUE;
         }
         case IDC_BUTTON_TEST_AC: {
-            DISPLAY_MODE mode = GetModeFromCB(hDlg, IDC_COMBO_AC);
-            TestDisplayMode(hDlg, &mode);
+            DISPLAY_MODE mode = GetModeFromCB(hComboAC);
+            TestDisplayMode(hDlg, NULL, &mode);
             return TRUE;
         }
         break;
@@ -208,18 +180,17 @@ enum TRAY_IDS {
 };
 
 static NOTIFYICONDATA nid;
-static HWND hWnd;
 static HMENU hMenu;
 
-static LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
+static LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
     switch (uMsg) {
     case WM_TRAYICON:
         if (lParam == WM_RBUTTONUP) {
             POINT pt;
             GetCursorPos(&pt);
-            SetForegroundWindow(hwnd); // Required for menu to disappear correctly
+            SetForegroundWindow(hWnd); // Required for menu to disappear correctly
 
-            TrackPopupMenu(hMenu, TPM_RIGHTBUTTON, pt.x, pt.y, 0, hwnd, NULL);
+            TrackPopupMenu(hMenu, TPM_RIGHTBUTTON, pt.x, pt.y, 0, hWnd, NULL);
         }
         break;
 
@@ -229,10 +200,10 @@ static LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM l
             DialogBox(GetModuleHandle(NULL), MAKEINTRESOURCE(IDD_PREFSDIALOG), hWnd, PrefsDialogProc);
             break;
         case ID_TRAY_ABOUT:
-            MessageBoxW(NULL, L"WinPowerDMS\nA utility for switching the resolution of your laptop's display based on the current power state.", L"About", MB_OK | MB_ICONINFORMATION);
+            MessageBoxW(hWnd, L"WinPowerDMS\nA utility for switching the resolution of your laptop's display based on the current power state.", L"About", MB_OK | MB_ICONINFORMATION);
             break;
         case ID_TRAY_EXIT:
-            DestroyWindow(hwnd);
+            DestroyWindow(hWnd);
             break;
         }
         break;
@@ -245,19 +216,28 @@ static LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM l
     case WM_POWERBROADCAST:
         if (LOWORD(wParam) == PBT_POWERSETTINGCHANGE) {
             OutputDebugString(L"Power status changed\n");
+            DISPLAY_MODE currentMode = GetCurrentDisplayMode();
             SYSTEM_POWER_STATUS powerStatus;
-            if (GetSystemPowerStatus(&powerStatus)) {
-                ChangeDisplayMode(powerStatus.ACLineStatus ? &modeAC : &modeBatt, CDS_UPDATEREGISTRY);
+            // Change display mode only if the current display mode is one of the configured options.
+            if (GetSystemPowerStatus(&powerStatus) &&
+                (DisplayModeEquals(&currentMode, &userPrefs.modeBatt) || DisplayModeEquals(&currentMode, &userPrefs.modeAC)))
+            {
+                ChangeDisplayMode(NULL, powerStatus.ACLineStatus ? &userPrefs.modeAC : &userPrefs.modeBatt, CDS_UPDATEREGISTRY);
             }
         }
         break;
     }
-    return DefWindowProc(hwnd, uMsg, wParam, lParam);
+    return DefWindowProc(hWnd, uMsg, wParam, lParam);
 }
 
-int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
-    // Initialize the controls
-    InitCommonControls();
+int WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nShowCmd) {
+    if (!LoadPrefs()) { // set both battery and AC to current display mode if there are no preferences set
+        DISPLAY_MODE currentMode = GetCurrentDisplayMode();
+        userPrefs.modeAC = currentMode;
+        userPrefs.modeBatt = currentMode;
+    }
+
+    InitCommonControls(); // Initialize modern controls
 
     WNDCLASS wc = { 0 };
     wc.lpfnWndProc = WindowProc;
@@ -266,7 +246,7 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
 
     RegisterClass(&wc);
 
-    hWnd = CreateWindowEx(0, L"TrayAppClass", NULL, 0, 0, 0, 0, 0,
+    HWND hWnd = CreateWindowEx(0, L"TrayAppClass", NULL, 0, 0, 0, 0, 0,
         HWND_MESSAGE, NULL, hInstance, NULL);
     RegisterPowerSettingNotification(hWnd, &GUID_ACDC_POWER_SOURCE, DEVICE_NOTIFY_WINDOW_HANDLE);
 
@@ -277,12 +257,13 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
     AppendMenu(hMenu, MF_STRING, ID_TRAY_EXIT, L"Exit");
 
     // Setup tray icon
+    HICON hTrayIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_APPICON));
     nid.cbSize = sizeof(NOTIFYICONDATA);
     nid.hWnd = hWnd;
     nid.uID = TRAY_ICON_ID;
     nid.uFlags = NIF_MESSAGE | NIF_ICON | NIF_TIP;
     nid.uCallbackMessage = WM_TRAYICON;
-    nid.hIcon = LoadIcon(NULL, IDI_APPLICATION); // Replace this with my own icon at some point
+    nid.hIcon = hTrayIcon;
     wcscpy_s(nid.szTip, sizeof(nid.szTip) / sizeof(nid.szTip[0]), L"WinPowerDMS");
 
     Shell_NotifyIcon(NIM_ADD, &nid);
@@ -294,5 +275,6 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
         DispatchMessage(&msg);
     }
 
+    DestroyIcon(hTrayIcon);
     return 0;
 }

WinPowerDMS/WinPowerDMS.vcxproj

@@ -79,9 +79,14 @@
       <ConformanceMode>true</ConformanceMode>
     </ClCompile>
     <Link>
-      <SubSystem>Console</SubSystem>
+      <SubSystem>Windows</SubSystem>
       <GenerateDebugInformation>true</GenerateDebugInformation>
+      <AdditionalDependencies>ComCtl32.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <MinimumRequiredVersion>6.0</MinimumRequiredVersion>
     </Link>
+    <Manifest>
+      <EnableDpiAwareness>true</EnableDpiAwareness>
+    </Manifest>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
@@ -93,9 +98,14 @@
       <ConformanceMode>true</ConformanceMode>
     </ClCompile>
     <Link>
-      <SubSystem>Console</SubSystem>
+      <SubSystem>Windows</SubSystem>
       <GenerateDebugInformation>true</GenerateDebugInformation>
+      <AdditionalDependencies>ComCtl32.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <MinimumRequiredVersion>6.0</MinimumRequiredVersion>
     </Link>
+    <Manifest>
+      <EnableDpiAwareness>true</EnableDpiAwareness>
+    </Manifest>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
     <ClCompile>
@@ -108,9 +118,10 @@
       <SubSystem>Windows</SubSystem>
       <GenerateDebugInformation>true</GenerateDebugInformation>
       <AdditionalDependencies>ComCtl32.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <MinimumRequiredVersion>6.0</MinimumRequiredVersion>
     </Link>
     <Manifest>
-      <EnableDpiAwareness>PerMonitorHighDPIAware</EnableDpiAwareness>
+      <EnableDpiAwareness>true</EnableDpiAwareness>
     </Manifest>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
@@ -123,19 +134,29 @@
       <ConformanceMode>true</ConformanceMode>
     </ClCompile>
     <Link>
-      <SubSystem>Console</SubSystem>
+      <SubSystem>Windows</SubSystem>
       <GenerateDebugInformation>true</GenerateDebugInformation>
+      <AdditionalDependencies>ComCtl32.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <MinimumRequiredVersion>6.0</MinimumRequiredVersion>
     </Link>
+    <Manifest>
+      <EnableDpiAwareness>true</EnableDpiAwareness>
+    </Manifest>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClCompile Include="DisplayMode.c" />
     <ClCompile Include="WinPowerDMS.c" />
   </ItemGroup>
   <ItemGroup>
+    <ClInclude Include="DisplayMode.h" />
     <ClInclude Include="resource.h" />
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="WinPowerDMS.rc" />
   </ItemGroup>
+  <ItemGroup>
+    <Image Include="WinPowerDMS.ico" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>

WinPowerDMS/WinPowerDMS.vcxproj.filters

@@ -15,7 +15,10 @@
     </Filter>
   </ItemGroup>
   <ItemGroup>
-    <ClCompile Include="main.c">
+    <ClCompile Include="WinPowerDMS.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="DisplayMode.c">
       <Filter>Source Files</Filter>
     </ClCompile>
   </ItemGroup>
@@ -23,10 +26,18 @@
     <ClInclude Include="resource.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="DisplayMode.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="WinPowerDMS.rc">
       <Filter>Resource Files</Filter>
     </ResourceCompile>
   </ItemGroup>
+  <ItemGroup>
+    <Image Include="WinPowerDMS.ico">
+      <Filter>Resource Files</Filter>
+    </Image>
+  </ItemGroup>
 </Project>

WinPowerDMS/resource.h

@@ -1,22 +1,27 @@
 //{{NO_DEPENDENCIES}}
 // Microsoft Visual C++ generated include file.
-// Used by PowerDMS.rc
+// Used by WinPowerDMS.rc
 //
 #define IDD_PREFSDIALOG                 101
+#define IDI_APPICON                     106
 #define IDC_COMBO_BATT                  1001
 #define IDC_COMBO_AC                    1002
 #define IDC_BUTTON_TEST_BATT            1003
 #define IDC_BUTTON_TEST_AC              1004
 #define IDC_BUTTON_APPLY                1005
 #define IDC_LIST1                       1006
+#define IDC_CHECK_STARTUP               1007
+#define IDC_COMBO_DISPLAY               1008
+#define IDC_CHECK_ENABLE_DISPLAY        1009
+#define IDC_CHECK_DISPLAY               1009
 
 // Next default values for new objects
 // 
 #ifdef APSTUDIO_INVOKED
 #ifndef APSTUDIO_READONLY_SYMBOLS
-#define _APS_NEXT_RESOURCE_VALUE        104
+#define _APS_NEXT_RESOURCE_VALUE        107
 #define _APS_NEXT_COMMAND_VALUE         40001
-#define _APS_NEXT_CONTROL_VALUE         1007
+#define _APS_NEXT_CONTROL_VALUE         1012
 #define _APS_NEXT_SYMED_VALUE           101
 #endif
 #endif