Viewport: Avoid calling platform functions when window is not created (apart from Platform_GetWindowDpiScale, documented as such). Main viewport situation is still ambiguous. (#1542)

imgui.cpp

@@ -3681,7 +3681,7 @@ void ImGui::EndFrame()
     IM_ASSERT(g.FrameScopeActive && "Forgot to call ImGui::NewFrame()");
 
     // Notify OS when our Input Method Editor cursor has moved (e.g. CJK inputs using Microsoft IME)
-    if (g.PlatformIO.Platform_SetImeInputPos && g.PlatformImePosViewport != NULL && ImLengthSqr(g.PlatformImePos - g.PlatformImeLastPos) > 0.0001f)
+    if (g.PlatformIO.Platform_SetImeInputPos && ImLengthSqr(g.PlatformImePos - g.PlatformImeLastPos) > 0.0001f && g.PlatformImePosViewport && g.PlatformImePosViewport->PlatformWindowCreated)
     {
         g.PlatformIO.Platform_SetImeInputPos(g.PlatformImePosViewport, g.PlatformImePos);
         g.PlatformImeLastPos = g.PlatformImePos;
@@ -7292,14 +7292,15 @@ static void ImGui::UpdateViewports()
             continue;
         }
 
+        const bool platform_funcs_available = (n == 0 || viewport->PlatformWindowCreated);
         if ((g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
         {
-            if (g.PlatformIO.Platform_GetWindowMinimized && (n == 0 || viewport->PlatformWindowCreated))
+            if (g.PlatformIO.Platform_GetWindowMinimized && platform_funcs_available)
                 viewport->PlatformWindowMinimized = 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->PlatformWindowMinimized)
+            if (!viewport->PlatformWindowMinimized && platform_funcs_available)
             {
                 if (viewport->PlatformRequestMove)
                     viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
@@ -7665,10 +7666,13 @@ void ImGui::UpdatePlatformWindows()
     if (g.PlatformIO.Platform_GetWindowFocus != NULL)
     {
         ImGuiViewportP* focused_viewport = NULL;
-        for (int i = 0; i < g.Viewports.Size && focused_viewport == NULL; i++)
-            if (g.Viewports[i]->PlatformUserData != NULL || g.Viewports[i]->PlatformHandle != NULL)
-                if (g.PlatformIO.Platform_GetWindowFocus(g.Viewports[i]))
-                    focused_viewport = g.Viewports[i];
+        for (int n = 0; n < g.Viewports.Size && focused_viewport == NULL; n++)
+        {
+            ImGuiViewportP* viewport = g.Viewports[n];
+            if (n == 0 || viewport->PlatformWindowCreated)
+                if (g.PlatformIO.Platform_GetWindowFocus(viewport))
+                    focused_viewport = viewport;
+        }
         if (focused_viewport && g.PlatformLastFocusedViewport != focused_viewport->ID)
         {
             if (focused_viewport->LastFrontMostStampCount != g.WindowsFrontMostStampCount)
@@ -7758,6 +7762,7 @@ void ImGui::DestroyPlatformWindow(ImGuiViewportP* viewport)
     viewport->PlatformHandle = NULL;
     viewport->RendererUserData = viewport->PlatformHandle = NULL;
     viewport->PlatformWindowCreated = false;
+    viewport->PlatformRequestClose = viewport->PlatformRequestMove = viewport->PlatformRequestResize = false;
 }
 
 void ImGui::DestroyPlatformWindows()

imgui.h

@@ -2107,8 +2107,8 @@ struct ImGuiPlatformIO
     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)
     void    (*Platform_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // (Optional) Call Present/SwapBuffers (platform side)
-    float   (*Platform_GetWindowDpiScale)(ImGuiViewport* vp);               // (Optional) DPI handling: Return DPI scale for this viewport. 1.0f = 96 DPI. (FIXME-DPI)
-    void    (*Platform_OnChangedViewport)(ImGuiViewport* vp);               // (Optional) DPI handling: Called during Begin() every time the viewport we are outputting into changes, so back-end has a chance to swap fonts to adjust style.
+    float   (*Platform_GetWindowDpiScale)(ImGuiViewport* vp);               // (Optional) [BETA] (FIXME-DPI) DPI handling: Return DPI scale for this viewport. 1.0f = 96 DPI. IMPORTANT: this will be called _before_ the window is created, in which case the implementation is expected to use the viewport->Pos/Size fields to estimate DPI value.
+    void    (*Platform_OnChangedViewport)(ImGuiViewport* vp);               // (Optional) [BETA] (FIXME-DPI) DPI handling: Called during Begin() every time the viewport we are outputting into changes, so back-end has a chance to swap fonts to adjust style.
     void    (*Platform_SetImeInputPos)(ImGuiViewport* vp, ImVec2 pos);      // (Optional) Set IME (Input Method Editor, e.g. for Asian languages) input position, so text preview appears over the imgui input box.
     int     (*Platform_CreateVkSurface)(ImGuiViewport* vp, ImU64 vk_inst, const void* vk_allocators, ImU64* out_vk_surface); // (Optional) For Renderer to call into Platform code
 

imgui_internal.h

@@ -848,7 +848,7 @@ struct ImGuiContext
 
     // Platform support
     ImVec2                  PlatformImePos, PlatformImeLastPos; // Cursor position request & last passed to the OS Input Method Editor
-    ImGuiViewport*          PlatformImePosViewport;
+    ImGuiViewportP*         PlatformImePosViewport;
 
     // Settings
     bool                           SettingsLoaded;