FramebufferDisplay: Don't set rotation via core_construct

jepler · jepler · commit 71c63c2812ce · 2020-09-01T11:00:22.000-05:00
The expectations of displayio.Display and frambufferio.FramebufferDisplay
are different when it comes to rotation.

In displayio.Display, if you call core_construct with a WxH = 64x32
and rotation=90, you get something that is 32 pixels wide and 64 pixels
tall in the LCD's coordinate system.

This is fine, as the existing definitions were written to work like this.
With framebuffer displays, however, the underlying framebuffer (such as
RGBMatrix) says "I am WxH pixels wide in my coordinate system" and the
constructor is given a rotation; when the rotation indicates a transpose
that means "exchange rows and columns, so that to the Groups displayed
on it, there is an effectively HxW pixel region for use".

Happily, we already have a set_rotation method.  Thus (modulo the time
spent debugging things anyway:) the fix is simple: Always request no
rotation from core_construct, then immediately fix up the rotation
to match what was requested.

Testing performed: 32x16 RGBMatrix on Metro M4 Express (but using
the Airlift firmware, as this is the configuration the error was reported
on):
 * initially construct display at 0, 90, 180, 270 degrees
 * later change angle to 0, 90, 180, 270 degrees
 * no garbled display
 * no safe mode crashes
diff --git a/shared-module/framebufferio/FramebufferDisplay.c b/shared-module/framebufferio/FramebufferDisplay.c
@@ -66,7 +66,7 @@ void common_hal_framebufferio_framebufferdisplay_construct(framebufferio_framebu
         ram_height,
         0,
         0,
-        rotation,
+        0, // rotation
         depth,
         fb_getter_default(get_grayscale, (depth < 8)),
         fb_getter_default(get_pixels_in_byte_share_row, false),
@@ -92,6 +92,10 @@ void common_hal_framebufferio_framebufferdisplay_construct(framebufferio_framebu
     self->native_frames_per_second = fb_getter_default(get_native_frames_per_second, 60);
     self->native_ms_per_frame = 1000 / self->native_frames_per_second;
 
+    if (rotation != 0) {
+        common_hal_framebufferio_framebufferdisplay_set_rotation(self, rotation);
+    }
+
     supervisor_start_terminal(self->core.width, self->core.height);
 
     // Set the group after initialization otherwise we may send pixels while we delay in
