Drags, Sliders: store initial value on activation, as a convenience for some mods. (#8223)

imgui.cpp

@@ -3927,6 +3927,7 @@ ImGuiContext::ImGuiContext(ImFontAtlas* shared_font_atlas)
     ActiveIdPreviousFrameIsAlive = false;
     ActiveIdPreviousFrameHasBeenEditedBefore = false;
     ActiveIdPreviousFrameWindow = NULL;
+    memset(&ActiveIdValueOnActivation, 0, sizeof(ActiveIdValueOnActivation));
     LastActiveId = 0;
     LastActiveIdTimer = 0.0f;
 

imgui_internal.h

@@ -2109,6 +2109,7 @@ struct ImGuiContext
     bool                    ActiveIdPreviousFrameIsAlive;
     bool                    ActiveIdPreviousFrameHasBeenEditedBefore;
     ImGuiWindow*            ActiveIdPreviousFrameWindow;
+    ImGuiDataTypeStorage    ActiveIdValueOnActivation;          // Backup of initial value at the time of activation. ONLY SET BY SPECIFIC WIDGETS: DragXXX and SliderXXX.
     ImGuiID                 LastActiveId;                       // Store the last non-zero ActiveId, useful for animation.
     float                   LastActiveIdTimer;                  // Store the last non-zero ActiveId timer since the beginning of activation, useful for animation.
 

imgui_widgets.cpp

@@ -2632,6 +2632,10 @@ bool ImGui::DragScalar(const char* label, ImGuiDataType data_type, void* p_data,
                 temp_input_is_active = true;
             }
 
+        // Store initial value (not used by main lib but available as a convenience but some mods e.g. to revert)
+        if (make_active)
+            memcpy(&g.ActiveIdValueOnActivation, p_data, DataTypeGetInfo(data_type)->Size);
+
         if (make_active && !temp_input_is_active)
         {
             SetActiveID(id, window);
@@ -3222,6 +3226,10 @@ bool ImGui::SliderScalar(const char* label, ImGuiDataType data_type, void* p_dat
             if ((clicked && g.IO.KeyCtrl) || (g.NavActivateId == id && (g.NavActivateFlags & ImGuiActivateFlags_PreferInput)))
                 temp_input_is_active = true;
 
+        // Store initial value (not used by main lib but available as a convenience but some mods e.g. to revert)
+        if (make_active)
+            memcpy(&g.ActiveIdValueOnActivation, p_data, DataTypeGetInfo(data_type)->Size);
+
         if (make_active && !temp_input_is_active)
         {
             SetActiveID(id, window);