1 files changed, 23 insertions, 0 deletions

diff --git a/src/uiLibrary.h b/src/uiLibrary.h
index 98719d7..f6faf01 100644
--- a/src/uiLibrary.h
+++ b/src/uiLibrary.h
@@ -6,8 +6,31 @@
 
 #include <font.h>
 
+#ifndef NDEBUG
+#include <stdio.h>
+#define UI_LOG(...) printf("[ui] " __VA_ARGS__ "\n")
+#else
+#define UI_LOG
+#endif
+
+/// Input handling of scrollbars.
+typedef struct uiScrollState {
+  int scrollbar_handle_y_start; // y-coordinate of the scrollbar handle at the
+                                // start of the scroll.
+  int  table_offset_start; // Row offset of a table at the start of the scroll.
+  bool scrolling;          // Whether a scrollbar is being dragged.
+} uiScrollState;
+
+/// Input handling of mouse-down events.
+typedef struct uiMouseDownState {
+  uiPtr   widget;      // The widget currently processing a mouse down event.
+  uiPoint start_point; // Mouse position when the mouse went down.
+} uiMouseDownState;
+
 typedef struct uiLibrary {
   FontAtlas*         font;
+  uiScrollState      scroll;
+  uiMouseDownState   mouse_down;
   uiMouseButtonState mouse_button_state[uiMouseButtonMax];
   uiWidgetEvent      widget_events[MaxWidgetEvents];
   int                num_widget_events;