Viewport: Added support for minimized window which caused problem when ImGuiBackendFlags_HasMouseHoveredViewport was not supported. (#1542) + todo

docs/TODO.txt

@@ -281,14 +281,18 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
 
  - examples: move ImGui::NewFrame() out of the backend _NewFrame() ?
  - viewport: make it possible to have no main/hosting viewport
+ - viewport: We set ImGuiViewportFlags_NoFocusOnAppearing in a way that is required for GLFW/SDL binding, but could be handled better without
+   on a custom e.g. Win32 bindings. It prevents newly dragged-out viewports from taking the focus, which makes ALT+F4 more ambiguous.
+ - viewport: not focusing newly undocked viewport means clicking back on previous one doesn't bring OS window to front.
  - viewport: with platform decoration enabled, platform may force constraint (e.g. minimum size)
  - viewport: use getfocus/setfocus api to synchronize imgui<>platform focus better (e.g imgui-side ctrl-tab can focus os window, OS initial setup and alt-tab can focus imgui window etc.)
  - viewport: store per-viewport/monitor DPI in .ini file so an application reload or main window changing DPI on reload can be properly patched for.
- - viewport: vulkan renderer implementation. 
+ - viewport: implicit Debug window can hog a zombie viewport (harmless, noisy?)
  - viewport: need to clarify how to use GetMousePos() from a user point of view.
  - platform: glfw: no support for ImGuiBackendFlags_HasMouseHoveredViewport. 
  - platform: sdl: no support for ImGuiBackendFlags_HasMouseHoveredViewport. maybe we could use SDL_GetMouseFocus() / SDL_WINDOW_MOUSE_FOCUS if imgui could fallback on its heuristic when NoInputs is set
  - platform: sdl: no refresh of monitor/display (SDL doesn't seem to have an event for it).
+ - platform: sdl: multi-viewport + minimized window seems to break mouse wheel events (at least under Win32).
 
  - inputs: we need an explicit flag about whether the imgui window is focused, to be able to distinguish focused key releases vs alt-tabbing all release behaviors.
  - inputs: rework IO system to be able to pass actual ordered/timestamped events. use an event queue? (~#335, #71)

examples/imgui_impl_glfw.cpp

@@ -548,6 +548,12 @@ static bool ImGui_ImplGlfw_GetWindowFocus(ImGuiViewport* viewport)
     return glfwGetWindowAttrib(data->Window, GLFW_FOCUSED) != 0;
 }
 
+static bool ImGui_ImplGlfw_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataGlfw* data = (ImGuiViewportDataGlfw*)viewport->PlatformUserData;
+    return glfwGetWindowAttrib(data->Window, GLFW_ICONIFIED) != 0;
+}
+
 #if GLFW_HAS_WINDOW_ALPHA
 static void ImGui_ImplGlfw_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
 {
@@ -668,6 +674,7 @@ static void ImGui_ImplGlfw_InitPlatformInterface()
     platform_io.Platform_GetWindowSize = ImGui_ImplGlfw_GetWindowSize;
     platform_io.Platform_SetWindowFocus = ImGui_ImplGlfw_SetWindowFocus;
     platform_io.Platform_GetWindowFocus = ImGui_ImplGlfw_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplGlfw_GetWindowMinimized;
     platform_io.Platform_SetWindowTitle = ImGui_ImplGlfw_SetWindowTitle;
     platform_io.Platform_RenderWindow = ImGui_ImplGlfw_RenderWindow;
     platform_io.Platform_SwapBuffers = ImGui_ImplGlfw_SwapBuffers;

examples/imgui_impl_sdl.cpp

@@ -10,6 +10,7 @@
 // Missing features:
 //  [ ] Platform: SDL2 handling of IME under Windows appears to be broken and it explicitly disable the regular Windows IME. You can restore Windows IME by compiling SDL with SDL_DISABLE_WINDOWS_IME.
 //  [ ] Platform: Gamepad support (need to use SDL_GameController API to fill the io.NavInputs[] value when ImGuiConfigFlags_NavEnableGamepad is set).
+//  [ ] Platform: Multi-viewport + Minimized windows seems to break mouse wheel events (at least under Windows).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
@@ -472,6 +473,12 @@ static bool ImGui_ImplSDL2_GetWindowFocus(ImGuiViewport* viewport)
     return (SDL_GetWindowFlags(data->Window) & SDL_WINDOW_INPUT_FOCUS) != 0;
 }
 
+static bool ImGui_ImplSDL2_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataSDL2* data = (ImGuiViewportDataSDL2*)viewport->PlatformUserData;
+    return (SDL_GetWindowFlags(data->Window) & SDL_WINDOW_MINIMIZED) != 0;
+}
+
 static void ImGui_ImplSDL2_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataSDL2* data = (ImGuiViewportDataSDL2*)viewport->PlatformUserData;
@@ -543,6 +550,7 @@ static void ImGui_ImplSDL2_InitPlatformInterface(SDL_Window* window, void* sdl_g
     platform_io.Platform_GetWindowSize = ImGui_ImplSDL2_GetWindowSize;
     platform_io.Platform_SetWindowFocus = ImGui_ImplSDL2_SetWindowFocus;
     platform_io.Platform_GetWindowFocus = ImGui_ImplSDL2_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplSDL2_GetWindowMinimized;
     platform_io.Platform_SetWindowTitle = ImGui_ImplSDL2_SetWindowTitle;
     platform_io.Platform_RenderWindow = ImGui_ImplSDL2_RenderWindow;
     platform_io.Platform_SwapBuffers = ImGui_ImplSDL2_SwapBuffers;

examples/imgui_impl_win32.cpp

@@ -536,6 +536,13 @@ static bool ImGui_ImplWin32_GetWindowFocus(ImGuiViewport* viewport)
     return ::GetActiveWindow() == data->Hwnd;
 }
 
+static bool ImGui_ImplWin32_GetWindowMinimized(ImGuiViewport* viewport)
+{
+    ImGuiViewportDataWin32* data = (ImGuiViewportDataWin32*)viewport->PlatformUserData;
+    IM_ASSERT(data->Hwnd != 0);
+    return ::IsIconic(data->Hwnd) != 0;
+}
+
 static void ImGui_ImplWin32_SetWindowTitle(ImGuiViewport* viewport, const char* title)
 {
     // ::SetWindowTextA() doesn't properly handle UTF-8 so we explicitely convert our string.
@@ -683,6 +690,7 @@ static void ImGui_ImplWin32_InitPlatformInterface()
     platform_io.Platform_GetWindowSize = ImGui_ImplWin32_GetWindowSize;
     platform_io.Platform_SetWindowFocus = ImGui_ImplWin32_SetWindowFocus;
     platform_io.Platform_GetWindowFocus = ImGui_ImplWin32_GetWindowFocus;
+    platform_io.Platform_GetWindowMinimized = ImGui_ImplWin32_GetWindowMinimized;
     platform_io.Platform_SetWindowTitle = ImGui_ImplWin32_SetWindowTitle;
     platform_io.Platform_SetWindowAlpha = ImGui_ImplWin32_SetWindowAlpha;
     platform_io.Platform_GetWindowDpiScale = ImGui_ImplWin32_GetWindowDpiScale;

imgui.cpp

@@ -7185,7 +7185,7 @@ static bool ImGui::GetWindowAlwaysWantOwnViewport(ImGuiWindow* window)
 static void ImGui::UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
 {
     ImGuiContext& g = *GImGui;
-    if (!(viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) || window->Viewport == viewport)
+    if (!(viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) || window->Viewport == viewport || viewport->PlatformIsMinimized)
         return;
     if (!viewport->GetRect().Contains(window->Rect()))
         return;
@@ -7228,7 +7228,7 @@ static ImGuiViewportP* FindViewportHoveredFromPlatformWindowStack(const ImVec2 m
     for (int n = 0; n < g.Viewports.Size; n++)
     {
         ImGuiViewportP* viewport = g.Viewports[n];
-        if (!(viewport->Flags & ImGuiViewportFlags_NoInputs) && viewport->GetRect().Contains(mouse_platform_pos))
+        if (!(viewport->Flags & ImGuiViewportFlags_NoInputs) && !viewport->PlatformIsMinimized && viewport->GetRect().Contains(mouse_platform_pos))
             if (best_candidate == NULL || best_candidate->LastFrontMostStampCount < viewport->LastFrontMostStampCount)
                 best_candidate = viewport;
     }
@@ -7277,12 +7277,18 @@ static void ImGui::UpdateViewports()
 
         if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
         {
+            if (g.PlatformIO.Platform_GetWindowMinimized && (n == 0 || viewport->CreatedPlatformWindow))
+                viewport->PlatformIsMinimized = g.PlatformIO.Platform_GetWindowMinimized(viewport);
+
             // Apply Position and Size (from Platform Window to ImGui) if requested. 
             // We do it early in the frame instead of waiting for UpdatePlatformWindows() to avoid a frame of lag when moving/resizing using OS facilities.
-            if (viewport->PlatformRequestMove)
+            if (!viewport->PlatformIsMinimized)
-                viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
+            {
-            if (viewport->PlatformRequestResize)
+                if (viewport->PlatformRequestMove)
-                viewport->Size = viewport->LastPlatformSize = g.PlatformIO.Platform_GetWindowSize(viewport);
+                    viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
+                if (viewport->PlatformRequestResize)
+                    viewport->Size = viewport->LastPlatformSize = g.PlatformIO.Platform_GetWindowSize(viewport);
+            }
 
             // Translate imgui windows when a Host Viewport has been moved
             ImVec2 delta = viewport->Pos - viewport->LastPos;
@@ -9866,7 +9872,8 @@ static void RenderViewportThumbnail(ImDrawList* draw_list, ImGuiViewportP* viewp
 
     ImVec2 scale = bb.GetSize() / viewport->Size;
     ImVec2 off = bb.Min - viewport->Pos * scale;
-    window->DrawList->AddRectFilled(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border, 0.40f));
+    float alpha_mul = viewport->PlatformIsMinimized ? 0.30f : 1.00f;
+    window->DrawList->AddRectFilled(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul * 0.40f));
     for (int i = 0; i != g.Windows.Size; i++)
     {
         ImGuiWindow* thumb_window = g.Windows[i];
@@ -9884,12 +9891,12 @@ static void RenderViewportThumbnail(ImDrawList* draw_list, ImGuiViewportP* viewp
         thumb_r_scaled.ClipWithFull(bb);
         title_r_scaled.ClipWithFull(bb);
         const bool window_is_focused = (g.NavWindow && thumb_window->RootWindowForTitleBarHighlight == g.NavWindow->RootWindowForTitleBarHighlight);
-        window->DrawList->AddRectFilled(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_WindowBg));
+        window->DrawList->AddRectFilled(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_WindowBg, alpha_mul));
-        window->DrawList->AddRectFilled(title_r_scaled.Min, title_r_scaled.Max, ImGui::GetColorU32(window_is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg));
+        window->DrawList->AddRectFilled(title_r_scaled.Min, title_r_scaled.Max, ImGui::GetColorU32(window_is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg, alpha_mul));
-        window->DrawList->AddRect(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_Border));
+        window->DrawList->AddRect(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul));
-        window->DrawList->AddText(g.Font, g.FontSize * 1.0f, title_r_scaled.Min, ImGui::GetColorU32(ImGuiCol_Text), thumb_window->Name, ImGui::FindRenderedTextEnd(thumb_window->Name));
+        window->DrawList->AddText(g.Font, g.FontSize * 1.0f, title_r_scaled.Min, ImGui::GetColorU32(ImGuiCol_Text, alpha_mul), thumb_window->Name, ImGui::FindRenderedTextEnd(thumb_window->Name));
     }
-    draw_list->AddRect(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border));
+    draw_list->AddRect(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul));
 }
 
 void ImGui::ShowViewportThumbnails()
@@ -10069,10 +10076,10 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                 ImGuiWindowFlags flags = viewport->Flags;
                 ImGui::BulletText("Pos: (%.0f,%.0f), Size: (%.0f,%.0f), Monitor: %d, DpiScale: %.0f%%", viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y, viewport->PlatformMonitor, viewport->DpiScale * 100.0f);
                 if (viewport->Idx > 0) { ImGui::SameLine(); if (ImGui::SmallButton("Reset Pos")) { viewport->Pos = ImVec2(200,200); if (viewport->Window) viewport->Window->Pos = ImVec2(200,200); } }
-                ImGui::BulletText("Flags: 0x%04X =%s%s%s%s%s", viewport->Flags,
+                ImGui::BulletText("Flags: 0x%04X =%s%s%s%s%s%s", viewport->Flags,
                     (flags & ImGuiViewportFlags_CanHostOtherWindows) ? " CanHostOtherWindows" : "", (flags & ImGuiViewportFlags_NoDecoration) ? " NoDecoration" : "",
                     (flags & ImGuiViewportFlags_NoFocusOnAppearing)  ? " NoFocusOnAppearing"  : "", (flags & ImGuiViewportFlags_NoInputs)     ? " NoInputs"     : "",
-                    (flags & ImGuiViewportFlags_NoRendererClear)     ? " NoRendererClear"     : "");
+                    (flags & ImGuiViewportFlags_NoRendererClear)     ? " NoRendererClear"     : "", viewport->PlatformIsMinimized ? ", PlatformIsMinimized" : "");
                 for (int layer_i = 0; layer_i < IM_ARRAYSIZE(viewport->DrawDataBuilder.Layers); layer_i++)
                     for (int draw_list_i = 0; draw_list_i < viewport->DrawDataBuilder.Layers[layer_i].Size; draw_list_i++)
                         Funcs::NodeDrawList(NULL, viewport, viewport->DrawDataBuilder.Layers[layer_i][draw_list_i], "DrawList");

imgui.h

@@ -2047,6 +2047,7 @@ struct ImGuiPlatformIO
     ImVec2  (*Platform_GetWindowSize)(ImGuiViewport* vp);
     void    (*Platform_SetWindowFocus)(ImGuiViewport* vp);                  // Move window to front and set input focus
     bool    (*Platform_GetWindowFocus)(ImGuiViewport* vp);
+    bool    (*Platform_GetWindowMinimized)(ImGuiViewport* vp);
     void    (*Platform_SetWindowTitle)(ImGuiViewport* vp, const char* title);
     void    (*Platform_SetWindowAlpha)(ImGuiViewport* vp, float alpha);     // (Optional) Setup window transparency
     void    (*Platform_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // (Optional) Setup for render (platform side)

imgui_internal.h

@@ -607,6 +607,7 @@ struct ImGuiViewportP : public ImGuiViewport
     float               Alpha;                    // Window opacity (when dragging dockable windows/viewports we make them transparent)
     float               LastAlpha;
     int                 PlatformMonitor;
+    bool                PlatformIsMinimized;
     ImGuiWindow*        Window;
     ImDrawList*         OverlayDrawList;          // For convenience, a draw list we can render to that's always rendered last (we use it to draw software mouse cursor when io.MouseDrawCursor is set)
     ImDrawData          DrawDataP;
@@ -615,7 +616,7 @@ struct ImGuiViewportP : public ImGuiViewport
     ImVec2              LastPlatformSize;
     ImVec2              LastRendererSize;
 
-    ImGuiViewportP()         { Idx = -1; LastFrameActive = LastFrameOverlayDrawList = LastFrontMostStampCount = -1; LastNameHash = 0; CreatedPlatformWindow = false; Alpha = LastAlpha = 1.0f; PlatformMonitor = INT_MIN; Window = NULL; OverlayDrawList = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
+    ImGuiViewportP()         { Idx = -1; LastFrameActive = LastFrameOverlayDrawList = LastFrontMostStampCount = -1; LastNameHash = 0; CreatedPlatformWindow = false; Alpha = LastAlpha = 1.0f; PlatformMonitor = INT_MIN; PlatformIsMinimized = false; Window = NULL; OverlayDrawList = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
     ~ImGuiViewportP()        { if (OverlayDrawList) IM_DELETE(OverlayDrawList); }
     ImRect  GetRect() const  { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
     ImVec2  GetCenter() const{ return ImVec2(Pos.x + Size.x * 0.5f, Pos.y + Size.y * 0.5f); }