Viewport: Added ImGuiViewportFlags_NoFocusOnClick + support in imgui_impl_win32. Made windows with no decoration always set the _NoFocus flags. (#1542, #2117)

Fix e.g. clicking on protruding combo box stealing highlight from parent window with decoration.

examples/example_win32_directx11/main.cpp

@@ -139,6 +139,10 @@ int main(int, char**)
     //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;
     io.ConfigFlags |= ImGuiConfigFlags_DpiEnableScaleFonts;     // FIXME-DPI: THIS CURRENTLY DOESN'T WORK AS EXPECTED. DON'T USE IN USER APP!
     io.ConfigFlags |= ImGuiConfigFlags_DpiEnableScaleViewports; // FIXME-DPI
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = false;
+    //io.ConfigDockingTabBarOnSingleWindows = true;
+    //io.ConfigDockingTransparentPayload = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();

examples/imgui_impl_win32.cpp

@@ -737,6 +737,10 @@ static LRESULT CALLBACK ImGui_ImplWin32_WndProcHandler_PlatformWindow(HWND hWnd,
         case WM_SIZE:
             viewport->PlatformRequestResize = true;
             break;
+        case WM_MOUSEACTIVATE:
+            if (viewport->Flags & ImGuiViewportFlags_NoFocusOnClick)
+                return MA_NOACTIVATE;
+            break;
         case WM_NCHITTEST:
             // Let mouse pass-through the window. This will allow the back-end to set io.MouseHoveredViewport properly (which is OPTIONAL).
             // The ImGuiViewportFlags_NoInputs flag is set while dragging a viewport, as want to detect the window behind the one we are dragging.

imgui.cpp

@@ -5520,6 +5520,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 viewport_flags |= ImGuiViewportFlags_NoTaskBarIcon;
             if (g.IO.ConfigViewportsNoDecoration || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
                 viewport_flags |= ImGuiViewportFlags_NoDecoration;
+            if ((viewport_flags & ImGuiViewportFlags_NoDecoration) && (viewport_flags & ImGuiViewportFlags_NoTaskBarIcon))
+                viewport_flags |= ImGuiViewportFlags_NoFocusOnAppearing | ImGuiViewportFlags_NoFocusOnClick;
 
             // We can overwrite viewport flags using ImGuiWindowClass (advanced users)
             // We don't default to the main viewport because.

imgui.h

@@ -2298,9 +2298,10 @@ enum ImGuiViewportFlags_
     ImGuiViewportFlags_NoDecoration             = 1 << 0,   // Platform Window: Disable platform decorations: title bar, borders, etc. (generally set all windows, but if ImGuiConfigFlags_ViewportsDecoration is set we only set this on popups/tooltips)
     ImGuiViewportFlags_NoTaskBarIcon            = 1 << 1,   // Platform Window: Disable platform task bar icon (generally set on popups/tooltips, or all windows if ImGuiConfigFlags_ViewportsNoTaskBarIcon is set)
     ImGuiViewportFlags_NoFocusOnAppearing       = 1 << 2,   // Platform Window: Don't take focus when created.
-    ImGuiViewportFlags_NoInputs                 = 1 << 3,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
-    ImGuiViewportFlags_NoRendererClear          = 1 << 4,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead (because we will fill it entirely).
-    ImGuiViewportFlags_TopMost                  = 1 << 5    // Platform Window: Display on top (for tooltips only)
+    ImGuiViewportFlags_NoFocusOnClick           = 1 << 3,   // Platform Window: Don't take focus when clicked on.
+    ImGuiViewportFlags_NoInputs                 = 1 << 4,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
+    ImGuiViewportFlags_NoRendererClear          = 1 << 5,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead (because we will fill it entirely).
+    ImGuiViewportFlags_TopMost                  = 1 << 6    // Platform Window: Display on top (for tooltips only)
 };
 
 // The viewports created and managed by imgui. The role of the platform back-end is to create the platform/OS windows corresponding to each viewport.