Viewport: Making the code a little more sturdy (flag changes) + added descriptions. (#1542)

imgui.cpp

@@ -7328,11 +7328,12 @@ static void ImGui::UpdateViewports()
             for (int window_n = 0; window_n < g.Windows.Size; window_n++)
                 if (g.Windows[window_n]->Viewport == viewport)
                     g.Windows[window_n]->Viewport = NULL;
+            if (viewport == g.MouseLastHoveredViewport) 
+                g.MouseLastHoveredViewport = NULL;
             g.Viewports.erase(g.Viewports.Data + n);
 
             // Destroy
-            if (viewport == g.MouseLastHoveredViewport) g.MouseLastHoveredViewport = NULL;
+            DestroyPlatformWindow(viewport); // In most circumstances the platform window will already be destroyed here.
-            IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
             IM_ASSERT(g.PlatformIO.Viewports.contains(viewport) == false);
             IM_DELETE(viewport);
             n--;
@@ -7616,13 +7617,7 @@ void ImGui::UpdatePlatformWindows()
         destroy_platform_window |= (viewport->Window && !IsWindowActiveAndVisible(viewport->Window));
         if (destroy_platform_window)
         {
-            if (viewport->CreatedPlatformWindow && g.PlatformIO.Renderer_DestroyWindow)
+            DestroyPlatformWindow(viewport);
-                g.PlatformIO.Renderer_DestroyWindow(viewport);
-            if (viewport->CreatedPlatformWindow && g.PlatformIO.Platform_DestroyWindow)
-                g.PlatformIO.Platform_DestroyWindow(viewport);
-            viewport->CreatedPlatformWindow = false;
-            IM_ASSERT(viewport->RendererUserData == NULL);
-            IM_ASSERT(viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
             continue;
         }
         if (viewport->LastFrameActive < g.FrameCount)
@@ -7782,22 +7777,28 @@ void ImGui::RenderPlatformWindowsDefault(void* platform_render_arg, void* render
     }
 }
 
+void ImGui::DestroyPlatformWindow(ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    if (viewport->CreatedPlatformWindow && g.PlatformIO.Renderer_DestroyWindow)
+        g.PlatformIO.Renderer_DestroyWindow(viewport);
+    if (viewport->CreatedPlatformWindow && g.PlatformIO.Platform_DestroyWindow)
+        g.PlatformIO.Platform_DestroyWindow(viewport);
+    viewport->CreatedPlatformWindow = false;
+    IM_ASSERT(viewport->RendererUserData == NULL);
+    IM_ASSERT(viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
+}
+
 void ImGui::DestroyPlatformWindows()
 {
     // We call the destroy window on the main viewport (index 0) to give a chance to the back-end to clear any data 
     // have stored in e.g. PlatformHandle.
-    // It is expected that the back-end stored a flag to remember that it doesn't own the window created for the main viewport, 
+    // It is expected that the back-end stored a flag to remember that it doesn't own the window created for the 
-    // and won't destroy the underlying platform/renderer data (e.g. 
+    // main viewport, and won't destroy the underlying platform/renderer data.
     ImGuiContext& g = *GImGui;
     for (int i = 0; i < g.Viewports.Size; i++)
         if (g.Viewports[i]->CreatedPlatformWindow)
-        {
+            DestroyPlatformWindow(g.Viewports[i]);
-            if (g.PlatformIO.Renderer_DestroyWindow)
-                g.PlatformIO.Renderer_DestroyWindow(g.Viewports[i]);
-            if (g.PlatformIO.Platform_DestroyWindow)
-                g.PlatformIO.Platform_DestroyWindow(g.Viewports[i]);
-            g.Viewports[i]->CreatedPlatformWindow = false;
-        }
 }
 
 //-----------------------------------------------------------------------------

imgui.h

@@ -880,7 +880,7 @@ enum ImGuiConfigFlags_
     // [BETA] Viewports
     ImGuiConfigFlags_ViewportsEnable        = 1 << 10,  // Viewport enable flags (require both ImGuiConfigFlags_PlatformHasViewports + ImGuiConfigFlags_RendererHasViewports set by the respective back-ends)
     ImGuiConfigFlags_ViewportsNoTaskBarIcons= 1 << 11,  // Disable task bars icons for all secondary viewports (will set ImGuiViewportFlags_NoTaskBarIcon on them)
-    ImGuiConfigFlags_ViewportsNoMerge       = 1 << 12,  // All floating windows _always_ have create their own viewport and platform window.
+    ImGuiConfigFlags_ViewportsNoMerge       = 1 << 12,  // All floating windows will always create their own viewport and platform window.
     ImGuiConfigFlags_DpiEnableScaleViewports= 1 << 13,  // FIXME-DPI: Reposition and resize imgui windows when the DpiScale of a viewport changed (mostly useful for the main viewport hosting other window). Note that resizing the main window itself is up to your application.
     ImGuiConfigFlags_DpiEnableScaleFonts    = 1 << 14,  // FIXME-DPI: Request bitmap-scaled fonts to match DpiScale. This is a very low-quality workaround. The correct way to handle DPI is _currently_ to replace the atlas and/or fonts in the Platform_OnChangedViewport callback, but this is all early work in progress.
 

imgui_demo.cpp

@@ -284,8 +284,11 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::CheckboxFlags("io.ConfigFlags: NoMouseCursorChange", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_NoMouseCursorChange);
             ImGui::SameLine(); ShowHelpMarker("Instruct back-end to not alter mouse cursor shape and visibility.");
             ImGui::CheckboxFlags("io.ConfigFlags: ViewportsEnable", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsEnable);
+            ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (it will offset your windows).");
             ImGui::CheckboxFlags("io.ConfigFlags: ViewportsNoTaskBarIcons", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsNoTaskBarIcons);
+            ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the task bar icon state right away).");
             ImGui::CheckboxFlags("io.ConfigFlags: ViewportsNoMerge", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsNoMerge);
+            ImGui::SameLine(); ShowHelpMarker("All floating windows will always create their own viewport and platform window.");
             ImGui::Checkbox("io.ConfigInputTextCursorBlink", &io.ConfigInputTextCursorBlink);
             ImGui::SameLine(); ShowHelpMarker("Set to false to disable blinking cursor, for users who consider it distracting");
             ImGui::Checkbox("io.ConfigResizeWindowsFromEdges [beta]", &io.ConfigResizeWindowsFromEdges);

imgui_internal.h

@@ -1199,6 +1199,7 @@ namespace ImGui
     // Viewports
     IMGUI_API ImGuiViewportP*       FindViewportByID(ImGuiID id);
     IMGUI_API void                  ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale);
+    IMGUI_API void                  DestroyPlatformWindow(ImGuiViewportP* viewport);
     IMGUI_API void                  ShowViewportThumbnails();
 
     // Settings