Viewports: Todos, Tooltips/menus not automatically forced into their own viewport when the NoMerge flag is set (however the multiplication of viewports makes them more likely to protude and create their own). Win32: try to make primary monitor the first tin the list. (#1542)

TODO.txt

@@ -258,6 +258,14 @@ 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: clamp windows position within monitors (especially important on monitor configuration change) -> clamp to closest rectangle.
+ - 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: 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: IME positioning are wrong.
+ - viewport: vulkan renderer implementation. 
+ - viewport: need to clarify how to use GetMousePos() from a user point of view.
+
  - inputs: we need an explicit flag about whether the imgui window is focused, to be able to distinguish focused key releases vs alt-tabbing all release behaviors.
  - inputs: rework IO system to be able to pass actual ordered/timestamped events. use an event queue? (~#335, #71)
  - inputs: support track pad style scrolling & slider edit.

imgui.cpp

@@ -3307,10 +3307,11 @@ static void SetWindowViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
 
 static bool GetWindowAlwaysWantOwnViewport(ImGuiWindow* window)
 {
+    // Tooltips and menus are not automatically forced into their own viewport when the NoMerge flag is set, however the multiplication of viewports makes them more likely to protude and create their own.
     ImGuiContext& g = *GImGui;
-    if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsNoMerge))
+    if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsNoMerge) && (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
         //if (window->DockStatus == ImGuiDockStatus_Floating)
-            if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_ChildMenu)) == 0)
+            if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip)) == 0)
                 return true;
     return false;
 }