Backends: GLFW, SDL: Platform monitors declared properly even if multi-viewport is not enabled.

examples/imgui_impl_glfw.cpp

@@ -83,11 +83,12 @@ static GLFWmousebuttonfun   g_PrevUserCallbackMousebutton = NULL;
 static GLFWscrollfun        g_PrevUserCallbackScroll = NULL;
 static GLFWkeyfun           g_PrevUserCallbackKey = NULL;
 static GLFWcharfun          g_PrevUserCallbackChar = NULL;
+static GLFWmonitorfun       g_PrevUserCallbackMonitor = NULL;
 
 // Forward Declarations
+static void ImGui_ImplGlfw_UpdateMonitors();
 static void ImGui_ImplGlfw_InitPlatformInterface();
 static void ImGui_ImplGlfw_ShutdownPlatformInterface();
-static void ImGui_ImplGlfw_UpdateMonitors();
 
 static const char* ImGui_ImplGlfw_GetClipboardText(void* user_data)
 {
@@ -149,6 +150,11 @@ void ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c)
     io.AddInputCharacter(c);
 }
 
+void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
+{
+    g_WantUpdateMonitors = true;
+}
+
 static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, GlfwClientApi client_api)
 {
     g_Window = window;
@@ -220,6 +226,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     g_PrevUserCallbackScroll = NULL;
     g_PrevUserCallbackKey = NULL;
     g_PrevUserCallbackChar = NULL;
+    g_PrevUserCallbackMonitor = NULL;
     if (install_callbacks)
     {
         g_InstalledCallbacks = true;
@@ -227,8 +234,13 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
         g_PrevUserCallbackScroll = glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
         g_PrevUserCallbackKey = glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
         g_PrevUserCallbackChar = glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
+        g_PrevUserCallbackMonitor = glfwSetMonitorCallback(ImGui_ImplGlfw_MonitorCallback);
     }
 
+    // Update monitors the first time (note: monitor callback are broken in GLFW 3.2 and earlier, see github.com/glfw/glfw/issues/784)
+    ImGui_ImplGlfw_UpdateMonitors();
+    glfwSetMonitorCallback(ImGui_ImplGlfw_MonitorCallback);
+
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
     main_viewport->PlatformHandle = (void*)g_Window;
@@ -405,6 +417,40 @@ static void ImGui_ImplGlfw_UpdateGamepads()
         io.BackendFlags &= ~ImGuiBackendFlags_HasGamepad;
 }
 
+static void ImGui_ImplGlfw_UpdateMonitors()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    int monitors_count = 0;
+    GLFWmonitor** glfw_monitors = glfwGetMonitors(&monitors_count);
+    platform_io.Monitors.resize(0);
+    for (int n = 0; n < monitors_count; n++)
+    {
+        ImGuiPlatformMonitor monitor;
+        int x, y;
+        glfwGetMonitorPos(glfw_monitors[n], &x, &y);
+        const GLFWvidmode* vid_mode = glfwGetVideoMode(glfw_monitors[n]);
+#if GLFW_HAS_MONITOR_WORK_AREA
+        monitor.MainPos = ImVec2((float)x, (float)y);
+        monitor.MainSize = ImVec2((float)vid_mode->width, (float)vid_mode->height);
+        int w, h;
+        glfwGetMonitorWorkarea(glfw_monitors[n], &x, &y, &w, &h);
+        monitor.WorkPos = ImVec2((float)x, (float)y);;
+        monitor.WorkSize = ImVec2((float)w, (float)h);
+#else
+        monitor.MainPos = monitor.WorkPos = ImVec2((float)x, (float)y);
+        monitor.MainSize = monitor.WorkSize = ImVec2((float)vid_mode->width, (float)vid_mode->height);
+#endif
+#if GLFW_HAS_PER_MONITOR_DPI
+        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
+        float x_scale, y_scale;
+        glfwGetMonitorContentScale(glfw_monitors[n], &x_scale, &y_scale);
+        monitor.DpiScale = x_scale;
+#endif
+        platform_io.Monitors.push_back(monitor);
+    }
+    g_WantUpdateMonitors = false;
+}
+
 void ImGui_ImplGlfw_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
@@ -746,45 +792,6 @@ static int ImGui_ImplGlfw_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_inst
 }
 #endif // GLFW_HAS_VULKAN
 
-static void ImGui_ImplGlfw_UpdateMonitors()
-{
-    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
-    int monitors_count = 0;
-    GLFWmonitor** glfw_monitors = glfwGetMonitors(&monitors_count);
-    platform_io.Monitors.resize(0);
-    for (int n = 0; n < monitors_count; n++)
-    {
-        ImGuiPlatformMonitor monitor;
-        int x, y;
-        glfwGetMonitorPos(glfw_monitors[n], &x, &y);
-        const GLFWvidmode* vid_mode = glfwGetVideoMode(glfw_monitors[n]);
-#if GLFW_HAS_MONITOR_WORK_AREA
-        monitor.MainPos = ImVec2((float)x, (float)y);
-        monitor.MainSize = ImVec2((float)vid_mode->width, (float)vid_mode->height);
-        int w, h;
-        glfwGetMonitorWorkarea(glfw_monitors[n], &x, &y, &w, &h);
-        monitor.WorkPos = ImVec2((float)x, (float)y);;
-        monitor.WorkSize = ImVec2((float)w, (float)h);
-#else
-        monitor.MainPos = monitor.WorkPos = ImVec2((float)x, (float)y);
-        monitor.MainSize = monitor.WorkSize = ImVec2((float)vid_mode->width, (float)vid_mode->height);
-#endif
-#if GLFW_HAS_PER_MONITOR_DPI
-        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
-        float x_scale, y_scale;
-        glfwGetMonitorContentScale(glfw_monitors[n], &x_scale, &y_scale);
-        monitor.DpiScale = x_scale;
-#endif
-        platform_io.Monitors.push_back(monitor);
-    }
-    g_WantUpdateMonitors = false;
-}
-
-static void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
-{
-    g_WantUpdateMonitors = true;
-}
-
 static void ImGui_ImplGlfw_InitPlatformInterface()
 {
     // Register platform interface (will be coupled with a renderer interface)
@@ -812,10 +819,6 @@ static void ImGui_ImplGlfw_InitPlatformInterface()
     platform_io.Platform_SetImeInputPos = ImGui_ImplWin32_SetImeInputPos;
 #endif
 
-    // Note: monitor callback are broken GLFW 3.2 and earlier (see github.com/glfw/glfw/issues/784)
-    ImGui_ImplGlfw_UpdateMonitors();
-    glfwSetMonitorCallback(ImGui_ImplGlfw_MonitorCallback);
-
     // Register main window handle (which is owned by the main application, not by us)
     // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();

examples/imgui_impl_glfw.h

@@ -20,6 +20,7 @@
 #pragma once
 
 struct GLFWwindow;
+struct GLFWmonitor;
 
 IMGUI_IMPL_API bool     ImGui_ImplGlfw_InitForOpenGL(GLFWwindow* window, bool install_callbacks);
 IMGUI_IMPL_API bool     ImGui_ImplGlfw_InitForVulkan(GLFWwindow* window, bool install_callbacks);
@@ -32,3 +33,4 @@ IMGUI_IMPL_API void     ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, i
 IMGUI_IMPL_API void     ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c);
+IMGUI_IMPL_API void     ImGui_ImplGlfw_MonitorCallback(GLFWmonitor* monitor, int event);

examples/imgui_impl_sdl.cpp

@@ -77,6 +77,7 @@ static bool         g_MouseCanUseGlobalState = true;
 static bool         g_UseVulkan = false;
 
 // Forward Declarations
+static void ImGui_ImplSDL2_UpdateMonitors();
 static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context);
 static void ImGui_ImplSDL2_ShutdownPlatformInterface();
 
@@ -222,6 +223,9 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window, void* sdl_gl_context)
         main_viewport->PlatformHandleRaw = info.info.win.window;
 #endif
 
+    // Update monitors
+    ImGui_ImplSDL2_UpdateMonitors();
+
     // We need SDL_CaptureMouse(), SDL_GetGlobalMouseState() from SDL 2.0.4+ to support multiple viewports.
     // We left the call to ImGui_ImplSDL2_InitPlatformInterface() outside of #ifdef to avoid unused-function warnings.
     if ((io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (io.BackendFlags & ImGuiBackendFlags_PlatformHasViewports))
@@ -405,6 +409,34 @@ static void ImGui_ImplSDL2_UpdateGamepads()
     #undef MAP_ANALOG
 }
 
+// FIXME-PLATFORM: SDL doesn't have an event to notify the application of display/monitor changes
+static void ImGui_ImplSDL2_UpdateMonitors()
+{
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Monitors.resize(0);
+    int display_count = SDL_GetNumVideoDisplays();
+    for (int n = 0; n < display_count; n++)
+    {
+        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
+        ImGuiPlatformMonitor monitor;
+        SDL_Rect r;
+        SDL_GetDisplayBounds(n, &r);
+        monitor.MainPos = monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.MainSize = monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+#if SDL_HAS_USABLE_DISPLAY_BOUNDS
+        SDL_GetDisplayUsableBounds(n, &r);
+        monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
+        monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
+#endif
+#if SDL_HAS_PER_MONITOR_DPI
+        float dpi = 0.0f;
+        if (!SDL_GetDisplayDPI(n, &dpi, NULL, NULL))
+            monitor.DpiScale = dpi / 96.0f;
+#endif
+        platform_io.Monitors.push_back(monitor);
+    }
+}
+
 void ImGui_ImplSDL2_NewFrame(SDL_Window* window)
 {
     ImGuiIO& io = ImGui::GetIO();
@@ -632,34 +664,6 @@ static int ImGui_ImplSDL2_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_inst
 }
 #endif // SDL_HAS_VULKAN
 
-// FIXME-PLATFORM: SDL doesn't have an event to notify the application of display/monitor changes
-static void ImGui_ImplSDL2_UpdateMonitors()
-{
-    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
-    platform_io.Monitors.resize(0);
-    int display_count = SDL_GetNumVideoDisplays();
-    for (int n = 0; n < display_count; n++)
-    {
-        // Warning: the validity of monitor DPI information on Windows depends on the application DPI awareness settings, which generally needs to be set in the manifest or at runtime.
-        ImGuiPlatformMonitor monitor;
-        SDL_Rect r;
-        SDL_GetDisplayBounds(n, &r);
-        monitor.MainPos = monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
-        monitor.MainSize = monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
-#if SDL_HAS_USABLE_DISPLAY_BOUNDS
-        SDL_GetDisplayUsableBounds(n, &r);
-        monitor.WorkPos = ImVec2((float)r.x, (float)r.y);
-        monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
-#endif
-#if SDL_HAS_PER_MONITOR_DPI
-        float dpi = 0.0f;
-        if (!SDL_GetDisplayDPI(n, &dpi, NULL, NULL))
-            monitor.DpiScale = dpi / 96.0f;
-#endif
-        platform_io.Monitors.push_back(monitor);
-    }
-}
-
 static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_gl_context)
 {
     // Register platform interface (will be coupled with a renderer interface)
@@ -689,8 +693,6 @@ static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_g
     SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
 #endif
 
-    ImGui_ImplSDL2_UpdateMonitors();
-
     // Register main window handle (which is owned by the main application, not by us)
     // This is mostly for simplicity and consistency, so that our code (e.g. mouse handling etc.) can use same logic for main and secondary viewports.
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();

examples/imgui_impl_win32.cpp

@@ -263,6 +263,33 @@ static void ImGui_ImplWin32_UpdateGamepads()
 #endif // #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
 }
 
+static BOOL CALLBACK ImGui_ImplWin32_UpdateMonitors_EnumFunc(HMONITOR monitor, HDC, LPRECT, LPARAM)
+{
+    MONITORINFO info = { 0 };
+    info.cbSize = sizeof(MONITORINFO);
+    if (!::GetMonitorInfo(monitor, &info))
+        return TRUE;
+    ImGuiPlatformMonitor imgui_monitor;
+    imgui_monitor.MainPos = ImVec2((float)info.rcMonitor.left, (float)info.rcMonitor.top);
+    imgui_monitor.MainSize = ImVec2((float)(info.rcMonitor.right - info.rcMonitor.left), (float)(info.rcMonitor.bottom - info.rcMonitor.top));
+    imgui_monitor.WorkPos = ImVec2((float)info.rcWork.left, (float)info.rcWork.top);
+    imgui_monitor.WorkSize = ImVec2((float)(info.rcWork.right - info.rcWork.left), (float)(info.rcWork.bottom - info.rcWork.top));
+    imgui_monitor.DpiScale = ImGui_ImplWin32_GetDpiScaleForMonitor(monitor);
+    ImGuiPlatformIO& io = ImGui::GetPlatformIO();
+    if (info.dwFlags & MONITORINFOF_PRIMARY)
+        io.Monitors.push_front(imgui_monitor);
+    else
+        io.Monitors.push_back(imgui_monitor);
+    return TRUE;
+}
+
+static void ImGui_ImplWin32_UpdateMonitors()
+{
+    ImGui::GetPlatformIO().Monitors.resize(0);
+    ::EnumDisplayMonitors(NULL, NULL, ImGui_ImplWin32_UpdateMonitors_EnumFunc, NULL);
+    g_WantUpdateMonitors = false;
+}
+
 void    ImGui_ImplWin32_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
@@ -764,33 +791,6 @@ static LRESULT CALLBACK ImGui_ImplWin32_WndProcHandler_PlatformWindow(HWND hWnd,
     return DefWindowProc(hWnd, msg, wParam, lParam);
 }
 
-static BOOL CALLBACK ImGui_ImplWin32_UpdateMonitors_EnumFunc(HMONITOR monitor, HDC, LPRECT, LPARAM)
-{
-    MONITORINFO info = { 0 };
-    info.cbSize = sizeof(MONITORINFO);
-    if (!::GetMonitorInfo(monitor, &info))
-        return TRUE;
-    ImGuiPlatformMonitor imgui_monitor;
-    imgui_monitor.MainPos = ImVec2((float)info.rcMonitor.left, (float)info.rcMonitor.top);
-    imgui_monitor.MainSize = ImVec2((float)(info.rcMonitor.right - info.rcMonitor.left), (float)(info.rcMonitor.bottom - info.rcMonitor.top));
-    imgui_monitor.WorkPos = ImVec2((float)info.rcWork.left, (float)info.rcWork.top);
-    imgui_monitor.WorkSize = ImVec2((float)(info.rcWork.right - info.rcWork.left), (float)(info.rcWork.bottom - info.rcWork.top));
-    imgui_monitor.DpiScale = ImGui_ImplWin32_GetDpiScaleForMonitor(monitor);
-    ImGuiPlatformIO& io = ImGui::GetPlatformIO();
-    if (info.dwFlags & MONITORINFOF_PRIMARY)
-        io.Monitors.push_front(imgui_monitor);
-    else
-        io.Monitors.push_back(imgui_monitor);
-    return TRUE;
-}
-
-static void ImGui_ImplWin32_UpdateMonitors()
-{
-    ImGui::GetPlatformIO().Monitors.resize(0);
-    ::EnumDisplayMonitors(NULL, NULL, ImGui_ImplWin32_UpdateMonitors_EnumFunc, NULL);
-    g_WantUpdateMonitors = false;
-}
-
 static void ImGui_ImplWin32_InitPlatformInterface()
 {
     WNDCLASSEX wcex;

imgui.cpp

@@ -15329,9 +15329,11 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         ImGui::Indent(ImGui::GetTreeNodeToLabelSpacing());
         ImGui::ShowViewportThumbnails();
         ImGui::Unindent(ImGui::GetTreeNodeToLabelSpacing());
-        if (g.PlatformIO.Monitors.Size > 0 && ImGui::TreeNode("Monitors", "Monitors (%d)", g.PlatformIO.Monitors.Size))
+        bool open = ImGui::TreeNode("Monitors", "Monitors (%d)", g.PlatformIO.Monitors.Size);
+        ImGui::SameLine();
+        MetricsHelpMarker("Dear ImGui uses monitor data:\n- to query DPI settings on a per monitor basis\n- to position popup/tooltips so they don't straddle monitors.");
+        if (open)
         {
-            ImGui::TextWrapped("(When viewports are enabled, imgui needs uses monitor data to position popup/tooltips so they don't straddle monitors.)");
             for (int i = 0; i < g.PlatformIO.Monitors.Size; i++)
             {
                 const ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[i];