Viewport: Made platform_io.Monitors mandatory for proper multi-viewport use.

imgui.cpp

@@ -3427,6 +3427,7 @@ void ImGui::NewFrame()
             IM_ASSERT(g.PlatformIO.Platform_SetWindowPos != NULL  && "Platform init didn't install handlers?");
             IM_ASSERT(g.PlatformIO.Platform_GetWindowSize != NULL  && "Platform init didn't install handlers?");
             IM_ASSERT(g.PlatformIO.Platform_SetWindowSize != NULL  && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Monitors.Size > 0 && "Platform init didn't setup Monitors list?");
             IM_ASSERT((g.Viewports[0]->PlatformUserData != NULL || g.Viewports[0]->PlatformHandle != NULL) && "Platform init didn't setup main viewport.");
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
             IM_ASSERT(g.IO.RenderDrawListsFn == NULL);  // Call ImGui::Render() then pass ImGui::GetDrawData() yourself to your render function!
@@ -10445,7 +10446,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         ImGui::Unindent(ImGui::GetTreeNodeToLabelSpacing());
         if (g.PlatformIO.Monitors.Size > 0 && ImGui::TreeNode("Monitors", "Monitors (%d)", g.PlatformIO.Monitors.Size))
         {
-            ImGui::TextWrapped("(When viewports are enabled, imgui optionally uses monitor data to position popup/tooltips so they don't straddle monitors.)");
+            ImGui::TextWrapped("(When viewports are enabled, imgui needs uses monitor data to position popup/tooltips so they don't straddle monitors.)");
             for (int i = 0; i < g.PlatformIO.Monitors.Size; i++)
             {
                 const ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[i];

imgui.h

@@ -2174,8 +2174,8 @@ struct ImFont
 // - if you are new to dear imgui and trying to integrate it into your engine, you should probably ignore this for now.
 //-----------------------------------------------------------------------------
 
-// (Optional) Represent the bounds of each connected monitor/display and their DPI
-// This is used for: multiple DPI support + clamping the position of popups and tooltips so they don't straddle multiple monitors.
+// (Optional) This is required when enabling multi-viewport. Represent the bounds of each connected monitor/display and their DPI. 
+// We use this information for multiple DPI support + clamping the position of popups and tooltips so they don't straddle multiple monitors.
 struct ImGuiPlatformMonitor
 {
     ImVec2  MainPos, MainSize;  // Coordinates of the area displayed on this monitor (Min = upper left, Max = bottom right)