Support scrolling by dragging scrollbars

4 files changed, 98 insertions, 38 deletions

diff --git a/src/widget/scrollbar.c b/src/widget/scrollbar.c
new file mode 100644
index 0000000..9cece5d
--- /dev/null
+++ b/src/widget/scrollbar.c
@@ -0,0 +1,8 @@
+#include "widget.h"
+
+int ScrollbarScroll(uiScrollbar* scrollbar, int y) {
+  assert(scrollbar);
+  scrollbar->handle_y =
+      Max(0, Min(scrollbar->height - scrollbar->handle_height, y));
+  return scrollbar->handle_y;
+}
diff --git a/src/widget/table.c b/src/widget/table.c
index 76a0413..e7d412e 100644
--- a/src/widget/table.c
+++ b/src/widget/table.c
@@ -1,20 +1,7 @@
 #include "widget.h"
 
-const uiCell* GetCell(const uiTable* table, int row, int col) {
-  assert(table);
-  return &table->cells[row][col];
-}
-
-uiCell* GetCellMut(uiTable* table, int row, int col) {
-  assert(table);
-  return (uiCell*)GetCell(table, row, col);
-}
-
-uiCell** GetLastRow(uiTable* table) {
-  assert(table);
-  assert(table->rows > 0);
-  return &table->cells[table->rows - 1];
-}
+#define Min(a, b) ((a) < (b) ? (a) : (b))
+#define Max(a, b) ((a) > (b) ? (a) : (b))
 
 uiTable* uiMakeTable(int rows, int cols, const char** header) {
   uiTable* table = UI_NEW(uiTable);
@@ -73,7 +60,7 @@ void uiTableAddRow(uiTable* table, const char** row) {
   ASSERT(cells);
   table->cells = cells;
 
-  uiCell** pLastRow = GetLastRow(table);
+  uiCell** pLastRow = TableGetLastRow(table);
   *pLastRow         = calloc(table->cols, sizeof(uiCell));
   ASSERT(*pLastRow);
   uiCell* lastRow = *pLastRow;
@@ -86,10 +73,45 @@ void uiTableAddRow(uiTable* table, const char** row) {
 void uiTableSet(uiTable* table, int row, int col, const char* text) {
   assert(table);
   assert(text);
-  GetCellMut(table, row, col)->text = string_new(text);
+  TableGetCellMut(table, row, col)->text = string_new(text);
 }
 
 const char* uiTableGet(const uiTable* table, int row, int col) {
   assert(table);
-  return string_data(GetCell(table, row, col)->text);
+  return string_data(TableGetCell(table, row, col)->text);
+}
+
+void uiTableScroll(uiTable* table, int row) {
+  assert(table);
+  table->offset = Min(table->rows - table->num_visible_rows, Max(0, row));
+  SyncScrollbarToTable(table);
+}
+
+void SyncScrollbarToTable(uiTable* table) {
+  assert(table);
+  ScrollbarScroll(
+      &table->scrollbar, (int)((double)table->offset / (double)table->rows *
+                               (double)table->height));
+}
+
+void SyncTableToScrollbar(uiTable* table) {
+  assert(table);
+  table->offset = (int)((double)table->scrollbar.handle_y /
+                        (double)table->height * (double)table->rows);
+}
+
+const uiCell* TableGetCell(const uiTable* table, int row, int col) {
+  assert(table);
+  return &table->cells[row][col];
+}
+
+uiCell* TableGetCellMut(uiTable* table, int row, int col) {
+  assert(table);
+  return (uiCell*)TableGetCell(table, row, col);
+}
+
+uiCell** TableGetLastRow(uiTable* table) {
+  assert(table);
+  assert(table->rows > 0);
+  return &table->cells[table->rows - 1];
 }
diff --git a/src/widget/widget.c b/src/widget/widget.c
index ef79ac4..ebcaf10 100644
--- a/src/widget/widget.c
+++ b/src/widget/widget.c
@@ -63,11 +63,28 @@ uiPtr uiMakeTablePtr(uiTable* table) {
   return (uiPtr){.type = uiTypeTable, .table = table};
 }
 
-static uiPtr uiMakeWidgetPtr(uiWidget* widget) {
+uiPtr uiMakeWidgetPtr(uiWidget* widget) {
   assert(widget);
-  return (uiPtr){.type = widget->type, .widget = widget};
+  switch (widget->type) {
+  case uiTypeButton:
+    return uiMakeButtonPtr((uiButton*)widget);
+  case uiTypeFrame:
+    return uiMakeFramePtr((uiFrame*)widget);
+  case uiTypeLabel:
+    return uiMakeLabelPtr((uiLabel*)widget);
+  case uiTypeTable:
+    return uiMakeTablePtr((uiTable*)widget);
+  default:
+    ASSERT(false);
+    break;
+  }
+  return (uiPtr){0};
 }
 
+uiPtr uiNullptr(void) { return (uiPtr){0}; }
+
+bool uiIsNullptr(uiPtr ptr) { return ptr.widget == 0; }
+
 uiButton* uiGetButtonPtr(uiPtr ptr) {
   assert(ptr.type == uiTypeButton);
   assert(ptr.button);
diff --git a/src/widget/widget.h b/src/widget/widget.h
index 63f3d94..db11164 100644
--- a/src/widget/widget.h
+++ b/src/widget/widget.h
@@ -16,39 +16,42 @@ typedef struct uiWidget {
   Widget_list  children;
 } uiWidget;
 
-/// Button.
 typedef struct uiButton {
   uiWidget widget;
   string   text;
 } uiButton;
 
-/// Frame.
 typedef struct uiFrame {
   uiWidget widget;
 } uiFrame;
 
-/// Label.
 typedef struct uiLabel {
   uiWidget widget;
   string   text;
 } uiLabel;
 
-/// Table cell.
+typedef struct uiScrollbar {
+  int width;
+  int height;        // Total height: handle plus scrollable area.
+  int handle_height; // Height of the scroll handle.
+  int handle_y;      // Starting y-coordinate of the handle.
+} uiScrollbar;
+
 typedef struct uiCell {
   string text;
 } uiCell;
 
-/// Table.
 typedef struct uiTable {
-  uiWidget widget;
-  int      rows;
-  int      cols;
-  int      height;           // Height in pixels.
-  int*     widths;           // Width, in pixels, for each column.
-  uiCell*  header;           // If non-null, row of 'cols' header cells.
-  uiCell** cells;            // Array of 'rows' rows, each of 'cols' cells.
-  int      offset;           // Offset into the rows of the table. Units: rows.
-  int      num_visible_rows; // The number of rows that are visible at once.
+  uiWidget    widget;
+  int         rows;
+  int         cols;
+  int         height; // Height in pixels.
+  int*        widths; // Width, in pixels, for each column.
+  uiCell*     header; // If non-null, row of 'cols' header cells.
+  uiCell**    cells;  // Array of 'rows' rows, each of 'cols' cells.
+  int         offset; // Offset into the rows of the table. Units: rows.
+  int         num_visible_rows; // The number of rows that are visible at once.
+  uiScrollbar scrollbar;
   struct {
     bool vertical_overflow : 1; // True if contents overflow vertically.
   } flags;
@@ -56,14 +59,24 @@ typedef struct uiTable {
 
 void DestroyWidget(uiWidget** ppWidget);
 
-const uiCell* GetCell(const uiTable* table, int row, int col);
-uiCell*       GetCellMut(uiTable* table, int row, int col);
-uiCell**      GetLastRow(uiTable* table);
+/// Set the scrollbar handle's y-coordinate, which is clipped to the scrollbar's
+/// rectangle.
+///
+/// Return the handle's y-coordinate after clipping.
+int ScrollbarScroll(uiScrollbar*, int y);
 
-#define UI_NEW(TYPE) (TYPE*)uiAlloc(1, sizeof(TYPE))
+const uiCell* TableGetCell(const uiTable*, int row, int col);
+uiCell*       TableGetCellMut(uiTable*, int row, int col);
+uiCell**      TableGetLastRow(uiTable*);
+void          SyncScrollbarToTable(uiTable*);
+void          SyncTableToScrollbar(uiTable*);
+
+static inline int Min(int a, int b) { return a < b ? a : b; }
+static inline int Max(int a, int b) { return a > b ? a : b; }
 
 static inline void* uiAlloc(size_t count, size_t size) {
   void* mem = calloc(count, size);
   ASSERT(mem);
   return mem;
 }
+#define UI_NEW(TYPE) (TYPE*)uiAlloc(1, sizeof(TYPE))