xF: make sure the caret is visible in X11 editor

xF.c

@@ -837,8 +837,8 @@ app_editor_position (void)
 	size_t position = 0;
 	for (int i = 0; i < g.editor.point; i++)
 	{
-		uint8_t encoded[6];
-		int len = u8_uctomb (encoded, g.editor.line[i], sizeof encoded);
+		uint8_t utf8[6];
+		int len = u8_uctomb (utf8, g.editor.line[i], sizeof utf8);
 		if (len > 0)
 			position += len;
 	}
@@ -1954,44 +1954,67 @@ tui_make_editor (chtype attrs)
 #ifdef WITH_X11
 
 static void
-x11_render_editor (struct widget *self)
+x11_process_editor (struct widget *self, int *x, int *caret, bool draw)
 {
-	x11_render_padding (self);
-
 	struct x11_font *font = x11_widget_font (self);
-	XftColor color = { .color = *x11_fg (self) };
+	XftColor fg = { .color = *x11_fg (self) }, bg = { .color = *x11_bg (self) };
 
-	// A simplistic adaptation of tui_render_editor() follows.
-	// TODO: Make this scroll around the caret, and fade like labels.
-	int x = self->x;
-	int caret = x;
 	for (size_t i = 0; i < g.editor.len; i++)
 	{
 		if ((int) i == g.editor.point)
-			caret = x;
+			*caret = *x;
 
 		ucs4_t codepoint = g.editor.line[i];
 		if (!iscntrl_ascii (codepoint))
 		{
-			uint8_t encoded[7] = {};
-			if (u8_uctomb (encoded, codepoint, sizeof encoded - 1) > 0)
-				x += x11_font_draw (font, &color, x, self->y, (char *) encoded);
+			uint8_t utf8[7] = {};
+			if (u8_uctomb (utf8, codepoint, sizeof utf8 - 1) > 0)
+				*x += draw
+					? x11_font_draw (font, &fg, *x, self->y, (char *) utf8)
+					: x11_font_hadvance (font, (char *) utf8);
 			continue;
 		}
 
 		char escaped[] = { '^', codepoint == 127 ? '?' : codepoint + 64, 0 };
 		int width = x11_font_hadvance (font, escaped);
-		XRenderFillRectangle (g_xui.dpy, PictOpSrc, g_xui.x11_pixmap_picture,
-			x11_fg (self), x, self->y, width, self->height);
-		XftColor reverse = { .color = *x11_bg (self) };
-		x += x11_font_draw (font, &reverse, x, self->y, escaped);
+		if (draw)
+		{
+			XftDrawRect (g_xui.xft_draw, &fg, *x, self->y, width, self->height);
+			*x += x11_font_draw (font, &bg, *x, self->y, escaped);
+		}
+		else
+			*x += width;
 	}
 	if (g.editor.point == (int) g.editor.len)
-		caret = x;
+		*caret = *x;
+}
+
+static void
+x11_render_editor (struct widget *self)
+{
+	enum { CARET_WIDTH = 2 };
+
+	int caret = 0, width = 0;
+	x11_process_editor (self, &width, &caret, false);
+
+	// Automatically scroll around the caret by changing where we start drawing:
+	int x = self->x, width_limit = self->width - CARET_WIDTH;
+	if (width > width_limit)
+	{
+		// Push it to the left until the caret is in the middle...
+		int offset = MAX (0, caret - width_limit / 2);
+		// ...but then push it to the right until text fills the whole width.
+		offset = MIN (offset, width - width_limit);
+
+		x -= offset;
+	}
+
+	x11_render_padding (self);
+	x11_process_editor (self, &x, &caret, true);
 
 	XRenderColor white = { 0xffff, 0xffff, 0xffff, 0xffff };
 	XRenderFillRectangle (g_xui.dpy, PictOpDifference, g_xui.x11_pixmap_picture,
-		&white, caret, self->y, 2, self->height);
+		&white, caret, self->y, CARET_WIDTH, self->height);
 }
 
 static struct widget *
@@ -2003,7 +2026,11 @@ x11_make_editor (chtype attrs)
 	widget->width = -1;
 	widget->height = g_xui.vunit;
 	widget->text = "";
-	return widget;
+
+	// Enforce clipping by putting this inside a container.
+	struct widget *wrapper = xui_hbox (widget);
+	wrapper->width = -1;
+	return wrapper;
 }
 
 static struct xui_scrollbar_part