Viewport: Avoid unnecessary reapplying platform pos/size every frame. (#2205) + Fix GLFW ImGui_ImplGlfw_CreateWindow() from not applying position immediately. Clear LastNameHash properly (bug already fixed in Docking branch)

examples/imgui_impl_glfw.cpp

@@ -409,6 +409,7 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     data->Window = glfwCreateWindow((int)viewport->Size.x, (int)viewport->Size.y, "No Title Yet", NULL, share_window);
     data->WindowOwned = true;
     viewport->PlatformHandle = (void*)data->Window;
+    glfwSetWindowPos(data->Window, (int)viewport->Pos.x, (int)viewport->Pos.y);
 
     // Install callbacks for secondary viewports
     glfwSetMouseButtonCallback(data->Window, ImGui_ImplGlfw_MouseButtonCallback);

imgui.cpp

@@ -7280,9 +7280,9 @@ static void ImGui::UpdateViewports()
             // 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)
-                viewport->Pos = g.PlatformIO.Platform_GetWindowPos(viewport);
+                viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
             if (viewport->PlatformRequestResize)
-                viewport->Size = g.PlatformIO.Platform_GetWindowSize(viewport);
+                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;
@@ -7576,18 +7576,21 @@ void ImGui::UpdatePlatformWindows()
             g.PlatformIO.Platform_CreateWindow(viewport);
             if (g.PlatformIO.Renderer_CreateWindow != NULL)
                 g.PlatformIO.Renderer_CreateWindow(viewport);
-            viewport->RendererLastSize = viewport->Size;
+            viewport->LastNameHash = 0;
+            viewport->LastPlatformPos = viewport->LastPlatformSize = ImVec2(FLT_MAX, FLT_MAX); // By clearing those we'll enforce a call to Platform_SetWindowPos/Platform_SetWindowSize before Platform_ShowWindow
+            viewport->LastRendererSize = viewport->Size;
             viewport->CreatedPlatformWindow = true;
         }
 
         // Apply Position and Size (from ImGui to Platform/Renderer back-ends)
-        if (!viewport->PlatformRequestMove)
+        if ((viewport->LastPlatformPos.x != viewport->Pos.x || viewport->LastPlatformPos.y != viewport->Pos.y) && !viewport->PlatformRequestMove)
             g.PlatformIO.Platform_SetWindowPos(viewport, viewport->Pos);
-        if (!viewport->PlatformRequestResize)
+        if ((viewport->LastPlatformSize.x != viewport->Size.x || viewport->LastPlatformSize.y != viewport->Size.y) && !viewport->PlatformRequestResize)
             g.PlatformIO.Platform_SetWindowSize(viewport, viewport->Size);
-        if (g.PlatformIO.Renderer_SetWindowSize && (viewport->RendererLastSize.x != viewport->Size.x || viewport->RendererLastSize.y != viewport->Size.y))
+        if ((viewport->LastRendererSize.x != viewport->Size.x || viewport->LastRendererSize.y != viewport->Size.y) && g.PlatformIO.Renderer_SetWindowSize)
             g.PlatformIO.Renderer_SetWindowSize(viewport, viewport->Size);
-        viewport->RendererLastSize = viewport->Size;
+        viewport->LastPlatformPos = viewport->Pos;
+        viewport->LastPlatformSize = viewport->LastRendererSize = viewport->Size;
 
         // Update title bar (if it changed)
         if (ImGuiWindow* window_for_title = viewport->Window)

imgui_internal.h

@@ -611,9 +611,11 @@ struct ImGuiViewportP : public ImGuiViewport
     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;
     ImDrawDataBuilder   DrawDataBuilder;
-    ImVec2              RendererLastSize;
+    ImVec2              LastPlatformPos;
+    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; RendererLastSize = ImVec2(-1.0f,-1.0f); }
+    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()        { 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); }