Viewports, Window: Avoid manually clipping resize grips and borders, which messes up with automation ability to locate the items. Also simpler and more standard.

Amend d8f9f6ba2abb6cfc00f704b887264ac9472cf9f7 and 377f7300546e2a43e225d38c724a7f28da0ed6f2.

imgui.cpp

@@ -5383,14 +5383,14 @@ static bool ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
     ImVec2 pos_target(FLT_MAX, FLT_MAX);
     ImVec2 size_target(FLT_MAX, FLT_MAX);
 
-    // Clip mouse interaction rectangles within the viewport (in practice the narrowing is going to happen most of the time).
+    // Clip mouse interaction rectangles within the viewport rectangle (in practice the narrowing is going to happen most of the time).
     // - Not narrowing would mostly benefit the situation where OS windows _without_ decoration have a threshold for hovering when outside their limits.
     //   This is however not the case with current back-ends under Win32, but a custom borderless window implementation would benefit from it.
     // - When decoration are enabled we typically benefit from that distance, but then our resize elements would be conflicting with OS resize elements, so we also narrow.
     // - Note that we are unable to tell if the platform setup allows hovering with a distance threshold (on Win32, decorated window have such threshold).
-    ImRect clip_viewport_rect(-FLT_MAX, -FLT_MAX, +FLT_MAX, +FLT_MAX);
-    if (!(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport) || (g.IO.MouseHoveredViewport != window->ViewportId) || !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration))
-        clip_viewport_rect = window->Viewport->GetRect();
+    const bool clip_with_viewport_rect = !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport) || (g.IO.MouseHoveredViewport != window->ViewportId) || !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration);
+    if (clip_with_viewport_rect)
+        PushClipRect(window->Viewport->Pos, window->Viewport->Pos + window->Viewport->Size, true); // Won't incur a draw command as we are not drawing here.
 
     // Resize grips and borders are on layer 1
     window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
@@ -5407,12 +5407,8 @@ static bool ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
         ImRect resize_rect(corner - grip.InnerDir * grip_hover_outer_size, corner + grip.InnerDir * grip_hover_inner_size);
         if (resize_rect.Min.x > resize_rect.Max.x) ImSwap(resize_rect.Min.x, resize_rect.Max.x);
         if (resize_rect.Min.y > resize_rect.Max.y) ImSwap(resize_rect.Min.y, resize_rect.Max.y);
-        ImVec2 resize_rect_ref_min = resize_rect.Min;
-        resize_rect.ClipWith(clip_viewport_rect);
         bool hovered, held;
         ButtonBehavior(resize_rect, window->GetID(resize_grip_n), &hovered, &held, ImGuiButtonFlags_FlattenChildren | ImGuiButtonFlags_NoNavFocus);
-        if (held && g.ActiveIdIsJustActivated)
-            g.ActiveIdClickOffset = g.IO.MousePos - resize_rect_ref_min; // Override our reference click offset as viewport clipping may be moved it.
         //GetForegroundDrawList(window)->AddRect(resize_rect.Min, resize_rect.Max, IM_COL32(255, 255, 0, 255));
         if (hovered || held)
             g.MouseCursor = (resize_grip_n & 1) ? ImGuiMouseCursor_ResizeNESW : ImGuiMouseCursor_ResizeNWSE;
@@ -5438,11 +5434,7 @@ static bool ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
     {
         bool hovered, held;
         ImRect border_rect = GetResizeBorderRect(window, border_n, grip_hover_inner_size, WINDOWS_RESIZE_FROM_EDGES_HALF_THICKNESS);
-        ImVec2 border_rect_ref_min = border_rect.Min;
-        border_rect.ClipWith(clip_viewport_rect);
         ButtonBehavior(border_rect, window->GetID(border_n + 4), &hovered, &held, ImGuiButtonFlags_FlattenChildren);
-        if (held && g.ActiveIdIsJustActivated)
-            g.ActiveIdClickOffset = g.IO.MousePos - border_rect_ref_min; // Override our reference click offset as viewport clipping may be moved it.
         //GetForegroundDrawLists(window)->AddRect(border_rect.Min, border_rect.Max, IM_COL32(255, 255, 0, 255));
         if ((hovered && g.HoveredIdTimer > WINDOWS_RESIZE_FROM_EDGES_FEEDBACK_TIMER) || held)
         {
@@ -5462,6 +5454,8 @@ static bool ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
         }
     }
     PopID();
+    if (clip_with_viewport_rect)
+        PopClipRect();
 
     // Restore nav layer
     window->DC.NavLayerCurrent = ImGuiNavLayer_Main;