lcd/skin_engine: Add the ability to draw onto the backdrop layer

The framebuffer the lcd driver uses can now be changed on the fly
which means that regular lcd_* drawing functions can draw onto the
"backdrop" buffer. The skin engine can use this to create layered
effects.

Add the tag %VB to a viewport to draw that viewport onto the
backdrop layer. If you want to draw an image onto the backdrop
framebuffer use %x(backdrop filename) instead of %X() inside
a viewport with %VB.

Change-Id: I741498e2af6d4f2d78932cabe8942317893e7cfc

1 files changed, 8 insertions, 0 deletions

diff --git a/firmware/drivers/lcd-bitmap-common.c b/firmware/drivers/lcd-bitmap-common.c
index f122e336d7..b0be687ed2 100644
--- a/firmware/drivers/lcd-bitmap-common.c
+++ b/firmware/drivers/lcd-bitmap-common.c
@@ -81,6 +81,14 @@ static void lcd_gradient_rect(int x1, int x2, int y, unsigned h,
 }
 #endif
 
+void LCDFN(set_framebuffer)(FBFN(data) *fb)
+{
+    if (fb)
+        LCDFN(framebuffer) = fb;
+    else
+        LCDFN(framebuffer) = &LCDFN(static_framebuffer)[0][0];
+}
+
 /*
  * draws the borders of the current viewport
  **/