TreeNode: Made clicking on arrow toggle toggle the open state on the Mouse Down event. Amend 05420ea2c.

docs/CHANGELOG.txt

@@ -45,6 +45,10 @@ Other Changes:
   where v_min == v_max. (#3361)
 - BeginMenuBar: Fixed minor bug where CursorPosMax gets pushed to CursorPos prior to calling BeginMenuBar(),
   so e.g. calling the function at the end of a window would often add +ItemSpacing.y to scrolling range.
+- TreeNode, CollapsingHeader: Made clicking on arrow toggle toggle the open state on the Mouse Down event 
+  rather than the Mouse Down+Up sequence, even if the _OpenOnArrow flag isn't set. This is standard behavior 
+  and amends the change done in 1.76 which only affected cases were _OpenOnArrow flag was set. 
+  (This is also necessary to support full multi/range-select/drag and drop operations.)
 - Metrics: Various tweaks, listing windows front-to-back, greying inactive items when possible.
 - Demo: Add simple InputText() callbacks demo (aside from the more elaborate ones in 'Examples->Console').
 

imgui.h

@@ -60,7 +60,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.79 WIP"
-#define IMGUI_VERSION_NUM           17802
+#define IMGUI_VERSION_NUM           17803
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 
 // Define attributes of all API symbols declarations (e.g. for DLL under Windows)

imgui_widgets.cpp

@@ -5644,17 +5644,14 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
 
     // Open behaviors can be altered with the _OpenOnArrow and _OnOnDoubleClick flags.
     // Some alteration have subtle effects (e.g. toggle on MouseUp vs MouseDown events) due to requirements for multi-selection and drag and drop support.
-    // - Single-click on label = Toggle on MouseUp (default)
-    // - Single-click on arrow = Toggle on MouseUp (when _OpenOnArrow=0)
+    // - Single-click on label = Toggle on MouseUp (default, when _OpenOnArrow=0)
+    // - Single-click on arrow = Toggle on MouseDown (when _OpenOnArrow=0)
     // - Single-click on arrow = Toggle on MouseDown (when _OpenOnArrow=1)
     // - Double-click on label = Toggle on MouseDoubleClick (when _OpenOnDoubleClick=1)
     // - Double-click on arrow = Toggle on MouseDoubleClick (when _OpenOnDoubleClick=1 and _OpenOnArrow=0)
-    // This makes _OpenOnArrow have a subtle effect on _OpenOnDoubleClick: arrow click reacts on Down rather than Up.
-    // It is rather standard that arrow click react on Down rather than Up and we'd be tempted to make it the default
-    // (by removing the _OpenOnArrow test below), however this would have a perhaps surprising effect on CollapsingHeader()?
-    // So right now we are making this optional. May evolve later.
+    // It is rather standard that arrow click react on Down rather than Up.
     // We set ImGuiButtonFlags_PressedOnClickRelease on OpenOnDoubleClick because we want the item to be active on the initial MouseDown in order for drag and drop to work.
-    if (is_mouse_x_over_arrow && (flags & ImGuiTreeNodeFlags_OpenOnArrow))
+    if (is_mouse_x_over_arrow)
         button_flags |= ImGuiButtonFlags_PressedOnClick;
     else if (flags & ImGuiTreeNodeFlags_OpenOnDoubleClick)
         button_flags |= ImGuiButtonFlags_PressedOnClickRelease | ImGuiButtonFlags_PressedOnDoubleClick;