Viewport: Removed unnecessary fields (now that the coordinate system is consistent accross viewports): MouseRefPrevViewport, MouseClickedPosViewportId. (#1542)

TODO.txt

@@ -258,8 +258,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - focus: SetKeyboardFocusHere() on with >= 0 offset could be done on same frame (else latch and modulate on beginning of next frame)
  - focus: unable to use SetKeyboardFocusHere() on clipped widgets. (#787)
 
- - viewport: popup/tooltip glitches when appearing near the monitor limits (e.g. opening a menu).
- - viewport: platform: introduce getfocus/setfocus api, so e.g. focus flags can be honored, imgui-side ctrl-tab can focus os window, OS alt-tab can focus imgui window etc.
+ - viewport: use getfocus/setfocus api to synchronize imgui<>platform focus better (e.g imgui-side ctrl-tab can focus os window, OS initial setup and alt-tab can focus imgui window etc.)
  - viewport: store per-viewport/monitor DPI in .ini file so an application reload or main window changing DPI on reload can be properly patched for.
  - viewport: vulkan renderer implementation. 
  - viewport: need to clarify how to use GetMousePos() from a user point of view.

examples/imgui_impl_win32.cpp

@@ -117,9 +117,9 @@ static bool ImGui_ImplWin32_UpdateMouseCursor()
 }
 
 // This code supports multiple OS Windows mapped into different ImGui viewports, 
-// So it is a little more complicated than your typical binding code (which only needs to set io.MousePos in your WM_MOUSEMOVE handler)
+// So it is a little more complicated than your typical single-viewport binding code (which only needs to set io.MousePos from the WM_MOUSEMOVE handler)
 // This is what imgui needs from the back-end to support multiple windows:
-// - io.MousePos               = mouse position (e.g. io.MousePos == viewport->Pos when we are on the upper-left of our viewport)
+// - io.MousePos               = mouse position in absolute coordinate (e.g. io.MousePos == ImVec2(0,0) when it is on the upper-left of the primary monitor)
 // - io.MousePosViewport       = viewport which mouse position is based from (generally the focused/active/capturing viewport)
 // - io.MouseHoveredWindow     = viewport which mouse is hovering, **regardless of it being the active/focused window**, **regardless of another window holding mouse captured**. [Optional]
 // This function overwrite the value of io.MousePos normally updated by the WM_MOUSEMOVE handler. 

imgui.cpp

@@ -3452,7 +3452,6 @@ static void ImGui::UpdateViewports()
     IM_ASSERT(g.PlatformIO.Viewports.Size <= g.Viewports.Size);
 
     // Update mouse reference viewport
-    g.MouseRefPrevViewport = g.MouseRefViewport;
     g.MouseRefViewport = g.IO.MousePosViewport ? FindViewportByID(g.IO.MousePosViewport) : g.Viewports[0];
 
     // Update main viewport with current platform position and size
@@ -3480,8 +3479,7 @@ static void ImGui::UpdateViewports()
 
             // Destroy
             if (viewport == g.MouseRefViewport)         g.MouseRefViewport = main_viewport;
-            if (viewport == g.MouseRefPrevViewport)     g.MouseRefPrevViewport = main_viewport;
-            if (viewport == g.MouseHoveredLastViewport) g.MouseHoveredLastViewport = NULL;
+            if (viewport == g.MouseLastHoveredViewport) g.MouseLastHoveredViewport = NULL;
             IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
             IM_ASSERT(g.PlatformIO.Viewports.contains(viewport) == false);
             IM_DELETE(viewport);
@@ -3531,7 +3529,7 @@ static void ImGui::UpdateViewports()
 
     if (!(g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
     {
-        g.MouseRefViewport = g.MouseRefPrevViewport = main_viewport;
+        g.MouseRefViewport = main_viewport;
         return;
     }
 
@@ -3555,7 +3553,7 @@ static void ImGui::UpdateViewports()
         viewport_hovered = FindViewportHoveredFromPlatformWindowStack(g.IO.MousePos);
     }
     if (viewport_hovered != NULL)
-        g.MouseHoveredLastViewport = viewport_hovered;
+        g.MouseLastHoveredViewport = viewport_hovered;
 
     // When dragging something, always refer to the last hovered viewport. 
     // (So when we are between viewports, our dragged preview will tend to show in the last viewport even if we don't have tooltips in viewports)
@@ -3564,7 +3562,7 @@ static void ImGui::UpdateViewports()
     if (is_mouse_dragging_with_an_expected_destination || g.ActiveId == 0 || !ImGui::IsAnyMouseDown())
     {
         if (is_mouse_dragging_with_an_expected_destination && viewport_hovered == NULL)
-            viewport_hovered = g.MouseHoveredLastViewport;
+            viewport_hovered = g.MouseLastHoveredViewport;
         if (viewport_hovered != NULL && viewport_hovered != g.MouseRefViewport && !(viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
             g.MouseRefViewport = viewport_hovered;
     }
@@ -3722,7 +3720,7 @@ static void ImGui::UpdateMouseInputs()
     ImGuiContext& g = *GImGui;
 
     // If mouse just appeared or disappeared (usually denoted by -FLT_MAX components) we cancel out movement in MouseDelta
-    if (IsMousePosValid(&g.IO.MousePos) && IsMousePosValid(&g.IO.MousePosPrev) && g.MouseRefViewport == g.MouseRefPrevViewport)
+    if (IsMousePosValid(&g.IO.MousePos) && IsMousePosValid(&g.IO.MousePosPrev))
         g.IO.MouseDelta = g.IO.MousePos - g.IO.MousePosPrev;
     else
         g.IO.MouseDelta = ImVec2(0.0f, 0.0f);
@@ -3752,7 +3750,6 @@ static void ImGui::UpdateMouseInputs()
             g.IO.MouseClickedPos[i] = g.IO.MousePos;
             g.IO.MouseDragMaxDistanceAbs[i] = ImVec2(0.0f, 0.0f);
             g.IO.MouseDragMaxDistanceSqr[i] = 0.0f;
-            g.MouseClickedPosViewportId[i] = g.MouseRefViewport->ID;
         }
         else if (g.IO.MouseDown[i])
         {
@@ -4198,7 +4195,7 @@ void ImGui::Shutdown(ImGuiContext* context)
     g.FontStack.clear();
     g.OpenPopupStack.clear();
     g.CurrentPopupStack.clear();
-    g.CurrentViewport = g.MouseRefViewport = g.MouseRefPrevViewport = g.MouseHoveredLastViewport = NULL;
+    g.CurrentViewport = g.MouseRefViewport = g.MouseLastHoveredViewport = NULL;
     for (int i = 0; i < g.Viewports.Size; i++)
         IM_DELETE(g.Viewports[i]);
     g.Viewports.clear();
@@ -5297,7 +5294,6 @@ ImVec2 ImGui::GetMouseDragDelta(int button, float lock_threshold)
         lock_threshold = g.IO.MouseDragThreshold;
     if (g.IO.MouseDown[button])
         if (g.IO.MouseDragMaxDistanceSqr[button] >= lock_threshold * lock_threshold)
-            if (g.MouseRefViewport->ID == g.MouseClickedPosViewportId[button])
             return g.IO.MousePos - g.IO.MouseClickedPos[button];     // Assume we can only get active with left-mouse button (at the moment).
     return ImVec2(0.0f, 0.0f);
 }

imgui_internal.h

@@ -642,9 +642,7 @@ struct ImGuiContext
     ImVector<ImGuiViewportP*> Viewports;                        // Active viewports (always 1+, and generally 1 unless multi-viewports are enabled). Each viewports hold their copy of ImDrawData. 
     ImGuiViewportP*         CurrentViewport;                    // We track changes of viewport (happening in Begin) so we can call Platform_OnChangedViewport()
     ImGuiViewportP*         MouseRefViewport;
-    ImGuiViewportP*         MouseRefPrevViewport;
-    ImGuiViewportP*         MouseHoveredLastViewport;           // Last viewport that was hovered by mouse (even if we are not hovering any viewport any more)
-    ImGuiID                 MouseClickedPosViewportId[5];       // For rarely used fields we only compare to, store viewport ID only so we don't have to clean dangling pointers
+    ImGuiViewportP*         MouseLastHoveredViewport;           // Last known viewport that was hovered by mouse (even if we are not hovering any viewport any more)
     ImGuiID                 PlatformLastFocusedViewport;        // Record of last focused platform window/viewport, when this changes we stamp the viewport as front-most
 
     // Navigation data (for gamepad/keyboard)
@@ -776,9 +774,7 @@ struct ImGuiContext
         NextTreeNodeOpenCond = 0;
 
         CurrentViewport = NULL;
-        MouseRefViewport = NULL;
-        MouseRefPrevViewport = MouseHoveredLastViewport = NULL;
-        memset(MouseClickedPosViewportId, 0, sizeof(MouseClickedPosViewportId));
+        MouseRefViewport = MouseLastHoveredViewport = NULL;
         PlatformLastFocusedViewport = 0;
 
         NavWindow = NULL;