Window, Inputs: Fixed resizing from edges when io.MousePos is not pix…

…el-rounded by rounding mouse position input. (#2110)

docs/CHANGELOG.txt

@@ -52,6 +52,7 @@ Other Changes:
 - Window: Resizing from edges (with io.ConfigResizeWindowsFromEdges Beta flag) extends the hit region
   of root floating windows outside the window, making it easier to resize windows. Resize grips are also
   extended accordingly so there are no discontinuity when hovering between borders and corners. (#1495, #822)
+- Window, Inputs: Fixed resizing from edges when io.MousePos is not pixel-rounded by rounding mouse position input. (#2110)
 - BeginChild(): Fixed BeginChild(const char*, ...) variation erroneously not applying the ID stack
   to the provided string to uniquely identify the child window. This was undoing an intentional change
   introduced in 1.50 and broken in 1.60. (#1698, #894, #713).

imgui.cpp

@@ -2933,6 +2933,10 @@ static void ImGui::UpdateMouseInputs()
 {
     ImGuiContext& g = *GImGui;
 
+    // Round mouse position to avoid spreading non-rounded position (e.g. UpdateManualResize doesn't support them well)
+    if (IsMousePosValid(&g.IO.MousePos))
+        g.IO.MousePos = ImFloor(g.IO.MousePos);
+
     // 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.IO.MouseDelta = g.IO.MousePos - g.IO.MousePosPrev;