video: Provide a signal when a new console line is started

When we start a new line (due to the user pressing return), signal this to
the driver so that it can flush its buffer of character positions.

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

drivers/video/vidconsole-uclass.c

@@ -47,6 +47,15 @@ int vidconsole_set_row(struct udevice *dev, uint row, int clr)
 	return ops->set_row(dev, row, clr);
 }
 
+static int vidconsole_entry_start(struct udevice *dev)
+{
+	struct vidconsole_ops *ops = vidconsole_get_ops(dev);
+
+	if (!ops->entry_start)
+		return -ENOSYS;
+	return ops->entry_start(dev);
+}
+
 /* Move backwards one space */
 static void vidconsole_back(struct udevice *dev)
 {
@@ -82,6 +91,8 @@ static void vidconsole_newline(struct udevice *dev)
 					   vid_priv->colour_bg);
 		priv->ycur -= rows * priv->y_charsize;
 	}
+	priv->last_ch = 0;
+
 	video_sync(dev->parent);
 }
 
@@ -99,6 +110,7 @@ int vidconsole_put_char(struct udevice *dev, char ch)
 		break;
 	case '\n':
 		vidconsole_newline(dev);
+		vidconsole_entry_start(dev);
 		break;
 	case '\t':	/* Tab (8 chars alignment) */
 		priv->xcur_frac = ((priv->xcur_frac / priv->tab_width_frac)
@@ -109,6 +121,7 @@ int vidconsole_put_char(struct udevice *dev, char ch)
 		break;
 	case '\b':
 		vidconsole_back(dev);
+		priv->last_ch = 0;
 		break;
 	default:
 		/*
@@ -125,6 +138,7 @@ int vidconsole_put_char(struct udevice *dev, char ch)
 		if (ret < 0)
 			return ret;
 		priv->xcur_frac += ret;
+		priv->last_ch = ch;
 		if (priv->xcur_frac >= priv->xsize_frac)
 			vidconsole_newline(dev);
 		break;

include/video_console.h

@@ -28,6 +28,7 @@
  * @tab_width_frac:	Tab width in fractional units
  * @xsize_frac:	Width of the display in fractional units
  * @xstart_frac:	Left margin for the text console in fractional units
+ * @last_ch:	Last character written to the text console on this line
  */
 struct vidconsole_priv {
 	struct stdio_dev sdev;
@@ -40,6 +41,7 @@ struct vidconsole_priv {
 	int tab_width_frac;
 	int xsize_frac;
 	int xstart_frac;
+	int last_ch;
 };
 
 /**
@@ -87,6 +89,18 @@ struct vidconsole_ops {
 	 * @return 0 if OK, -ve on error
 	 */
 	int (*set_row)(struct udevice *dev, uint row, int clr);
+
+	/**
+	 * entry_start() - Indicate that text entry is starting afresh
+	 *
+	 * Consoles which use proportional fonts need to track the position of
+	 * each character output so that backspace will return to the correct
+	 * place. This method signals to the console driver that a new entry
+	 * line is being start (e.g. the user pressed return to start a new
+	 * command). The driver can use this signal to empty its list of
+	 * positions.
+	 */
+	int (*entry_start)(struct udevice *dev);
 };
 
 /* Get a pointer to the driver operations for a video console device */