console: Allow measuring the bounding box of text

For laying out text accurately it is necessary to know the width and
height of the text. Add a measure() method to the console API, so this
can be supported.

Add an implementation for truetype and a base implementation for the
normal console.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/video/console_truetype.c

@@ -614,8 +614,8 @@ static void select_metrics(struct udevice *dev, struct console_tt_metrics *met)
 	vc_priv->tab_width_frac = VID_TO_POS(met->font_size) * 8 / 2;
 }
 
-static int truetype_select_font(struct udevice *dev, const char *name,
-				uint size)
+static int get_metrics(struct udevice *dev, const char *name, uint size,
+		       struct console_tt_metrics **metp)
 {
 	struct console_tt_priv *priv = dev_get_priv(dev);
 	struct console_tt_metrics *met;
@@ -653,11 +653,70 @@ static int truetype_select_font(struct udevice *dev, const char *name,
 		met = priv->metrics;
 	}
 
+	*metp = met;
+
+	return 0;
+}
+
+static int truetype_select_font(struct udevice *dev, const char *name,
+				uint size)
+{
+	struct console_tt_metrics *met;
+	int ret;
+
+	ret = get_metrics(dev, name, size, &met);
+	if (ret)
+		return log_msg_ret("sel", ret);
+
 	select_metrics(dev, met);
 
 	return 0;
 }
 
+int truetype_measure(struct udevice *dev, const char *name, uint size,
+		     const char *text, struct vidconsole_bbox *bbox)
+{
+	struct console_tt_metrics *met;
+	stbtt_fontinfo *font;
+	int lsb, advance;
+	const char *s;
+	int width;
+	int last;
+	int ret;
+
+	ret = get_metrics(dev, name, size, &met);
+	if (ret)
+		return log_msg_ret("sel", ret);
+
+	bbox->valid = false;
+	if (!*text)
+		return 0;
+
+	font = &met->font;
+	width = 0;
+	for (last = 0, s = text; *s; s++) {
+		int ch = *s;
+
+		/* Used kerning to fine-tune the position of this character */
+		if (last)
+			width += stbtt_GetCodepointKernAdvance(font, last, ch);
+
+		/* First get some basic metrics about this character */
+		stbtt_GetCodepointHMetrics(font, ch, &advance, &lsb);
+
+		width += advance;
+		last = ch;
+	}
+
+	bbox->valid = true;
+	bbox->x0 = 0;
+	bbox->y0 = 0;
+	bbox->x1 = tt_ceil((double)width * met->scale);
+	bbox->y1 = met->font_size;
+
+	return 0;
+}
+
 const char *console_truetype_get_font_size(struct udevice *dev, uint *sizep)
 {
 	struct console_tt_priv *priv = dev_get_priv(dev);
@@ -709,6 +768,7 @@ struct vidconsole_ops console_truetype_ops = {
 	.get_font	= console_truetype_get_font,
 	.get_font_size	= console_truetype_get_font_size,
 	.select_font	= truetype_select_font,
+	.measure	= truetype_measure,
 };
 
 U_BOOT_DRIVER(vidconsole_truetype) = {

drivers/video/vidconsole-uclass.c

@@ -596,6 +596,28 @@ int vidconsole_select_font(struct udevice *dev, const char *name, uint size)
 	return ops->select_font(dev, name, size);
 }
 
+int vidconsole_measure(struct udevice *dev, const char *name, uint size,
+		       const char *text, struct vidconsole_bbox *bbox)
+{
+	struct vidconsole_priv *priv = dev_get_uclass_priv(dev);
+	struct vidconsole_ops *ops = vidconsole_get_ops(dev);
+	int ret;
+
+	if (ops->select_font) {
+		ret = ops->measure(dev, name, size, text, bbox);
+		if (ret != -ENOSYS)
+			return ret;
+	}
+
+	bbox->valid = true;
+	bbox->x0 = 0;
+	bbox->y0 = 0;
+	bbox->x1 = priv->x_charsize * strlen(text);
+	bbox->y1 = priv->y_charsize;
+
+	return 0;
+}
+
 void vidconsole_push_colour(struct udevice *dev, enum colour_idx fg,
 			    enum colour_idx bg, struct vidconsole_colour *old)
 {

include/video_console.h

@@ -82,6 +82,27 @@ struct vidconsole_colour {
 	u32 colour_bg;
 };
 
+/**
+ * struct vidconsole_bbox - Bounding box of text
+ *
+ * This describes the bounding box of something, measured in pixels. The x0/y0
+ * pair is inclusive; the x1/y2 pair is exclusive, meaning that it is one pixel
+ * beyond the extent of the object
+ *
+ * @valid: Values are valid (bounding box is known)
+ * @x0: left x position, in pixels from left side
+ * @y0: top y position, in pixels from top
+ * @x1: right x position + 1
+ * @y1: botton y position + 1
+ */
+struct vidconsole_bbox {
+	bool valid;
+	int x0;
+	int y0;
+	int x1;
+	int y1;
+};
+
 /**
  * struct vidconsole_ops - Video console operations
  *
@@ -189,6 +210,20 @@ struct vidconsole_ops {
 	 * Returns: 0 on success, -ENOENT if no such font
 	 */
 	int (*select_font)(struct udevice *dev, const char *name, uint size);
+
+	/**
+	 * measure() - Measure the bounds of some text
+	 *
+	 * @dev:	Device to adjust
+	 * @name:	Font name to use (NULL to use default)
+	 * @size:	Font size to use (0 to use default)
+	 * @text:	Text to measure
+	 * @bbox:	Returns bounding box of text, assuming it is positioned
+	 *		at 0,0
+	 * Returns: 0 on success, -ENOENT if no such font
+	 */
+	int (*measure)(struct udevice *dev, const char *name, uint size,
+		       const char *text, struct vidconsole_bbox *bbox);
 };
 
 /* Get a pointer to the driver operations for a video console device */
@@ -215,6 +250,19 @@ int vidconsole_get_font(struct udevice *dev, int seq,
  */
 int vidconsole_select_font(struct udevice *dev, const char *name, uint size);
 
+/*
+ * vidconsole_measure() - Measuring the bounding box of some text
+ *
+ * @dev: Console device to use
+ * @name: Font name, NULL for default
+ * @size: Font size, ignored if @name is NULL
+ * @text: Text to measure
+ * @bbox: Returns nounding box of text
+ * Returns: 0 if OK, -ve on error
+ */
+int vidconsole_measure(struct udevice *dev, const char *name, uint size,
+		       const char *text, struct vidconsole_bbox *bbox);
+
 /**
  * vidconsole_push_colour() - Temporarily change the font colour
  *