From: Simon Glass <sjg@chromium.org> Provide a few notes about how the cursor works in the video console. Signed-off-by: Simon Glass <sjg@chromium.org> --- include/video_console.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/include/video_console.h b/include/video_console.h index 9005e9f4442..ac04aeb3aef 100644 --- a/include/video_console.h +++ b/include/video_console.h @@ -29,6 +29,26 @@ enum { * The cursor is set up and maintained by the vidconsole. It is a simple * vertical bar of width VIDCONSOLE_CURSOR_WIDTH shown in the foreground colour. * + * No cursor processing is done unless @enabled is true. + * + * To figure out where to draw the cursor, the vidconsole's get_cursor_info() is + * called. It fills in the @x, @y, @height and @index information below. That + * information remains valid while the cursor is shown, so it can be used to + * hide the cursor. + * + * The cursor is drawn only when idle (by vidconsole_show_cursor() called from + * vidconsole_idle()). It is erased as soon as any output needs to be written to + * the display - vidconsole_hide_cursor() is called from a few places in the + * vidconsole uclass. + * + * Under the hood, vidconsole_show_cursor() calls cursor_show() which saves the + * pixels under the cursor as it draws it. Once finished it sets @visible to + * true, so that we know we must erase the cursor before drawing anything else. + * + * The old pixels end up in @save_data and are used by cursor_hide() (called + * from vidconsole_hide_cursor()) to restore the display contents to what they + * were. Once that is done, @visible is set back to false. + * * @enabled: cursor is active (e.g. during readline) * @visible: cursor is currently visible * @indent: indent subsequent lines to the same position as the first line -- 2.43.0