jwidget: add a per-widget clipping setting

include/justui/jwidget.h

@@ -89,8 +89,10 @@ typedef struct jwidget {
 	uint visible        :1;
 	/* Widget is floating outside the layout (and positioned manually) */
 	uint floating       :1;
+	/* Widget is clipped during rendering */
+	uint clipped        :1;
 
-	uint :23;
+	uint :22;
 
 } jwidget;
 
@@ -358,6 +360,23 @@ bool jwidget_visible(void *w);
 /* jwidget_set_visible(): Hide or show a widget */
 void jwidget_set_visible(void *w, bool visible);
 
+/* jwidget_clipped(): Whether widget is clipped
+
+   If a widget is clipped then its rendering function cannot draw pixels
+   outside of its bounding box. There is no performance cost to this feature
+   because it relies on underlying gint rendering functions already supporting
+   clipping.
+
+   This is disabled by default because it is convenient to have widgets draw
+   outside their bounding box. For instance it is easier to align a single-
+   line label by setting the font's bearing as its height, and then drawing
+   glyphs' tails outside the bouding box. It is also harder to spot layout
+   issues if the widgets are clipped away. */
+bool jwidget_clipped(void *w);
+
+/* jwidget_set_clipped(): Set a widget's rendering clipping preference */
+void jwidget_set_clipped(void *w, bool clipped);
+
 /* jwidget_needs_update(): Check whether the tree needs to be re-rendered
 
    If this function returns true, you should re-render the tree. Aditionally,

src/jwidget.c

@@ -109,6 +109,7 @@ void jwidget_init(jwidget *w, int type, void *parent)
 	w->dirty = 1;
 	w->visible = 1;
 	w->floating = 0;
+	w->clipped = 0;
 
 	w->type = type;
 	w->geometry = NULL;
@@ -597,6 +598,21 @@ void jwidget_set_floating(void *w0, bool floating)
 	if(w->parent) w->parent->dirty = 1;
 }
 
+bool jwidget_clipped(void *w0)
+{
+	J_CAST(w)
+	return w->clipped;
+}
+
+void jwidget_set_clipped(void *w0, bool clipped)
+{
+	J_CAST(w)
+	if(w->clipped == clipped) return;
+
+	w->clipped = (clipped != 0);
+	w->update = 1;
+}
+
 //---
 // Rendering
 //---
@@ -643,7 +659,18 @@ void jwidget_render(void *w0, int x, int y)
 	y += g->margin.top  + b.top  + g->padding.top;
 
 	jwidget_poly const *poly = widget_types[w->type];
-	if(poly->render) poly->render(w, x, y);
+	if(poly->render) {
+		if(w->clipped) {
+			struct dwindow win = { x, y, x+cw, y+ch };
+			win = intersect_dwindow(win, dwindow);
+			struct dwindow old_window = dwindow_set(win);
+			poly->render(w, x, y);
+			dwindow_set(old_window);
+		}
+		else {
+			poly->render(w, x, y);
+		}
+	}
 
 	w->update = 0;
 }

src/util.h

@@ -6,6 +6,7 @@
 #define _J_UTIL
 
 #include <justui/defs.h>
+#include <gint/display.h>
 
 /* Clamp a value between two ends. */
 __attribute__((always_inline))
@@ -20,4 +21,16 @@ static inline int clamp(int value, int min, int max)
 /* Code point for a character input */
 uint32_t keymap_translate(int key, bool shift, bool alpha);
 
+/* Intersect two dwindow settings. */
+static inline struct dwindow intersect_dwindow(
+	struct dwindow d1, struct dwindow d2)
+{
+	struct dwindow win;
+	win.left   = max(d1.left, d2.left);
+	win.top    = max(d1.top, d2.top);
+	win.right  = max(min(d1.right, d2.right), win.left);
+	win.bottom = max(min(d1.bottom, d2.bottom), win.top);
+	return win;
+}
+
 #endif /* _J_UTIL */