Track a dirty area for in-memory bitmaps

This fixes the bug that bitmap changes do not cause screen updates
and optimizes the refresh when the bitmap is simply shown on the
screen. If the bitmap is used in tiles, then changing it will
cause all TileGrids using it to do a full refresh.

Fixes #1981

1 files changed, 38 insertions, 0 deletions

diff --git a/shared-module/displayio/Bitmap.c b/shared-module/displayio/Bitmap.c
index f8dc24c15..59971d25c 100644
--- a/shared-module/displayio/Bitmap.c
+++ b/shared-module/displayio/Bitmap.c
@@ -63,6 +63,11 @@ void common_hal_displayio_bitmap_construct(displayio_bitmap_t *self, uint32_t wi
     }
     self->x_mask = (1 << self->x_shift) - 1; // Used as a modulus on the x value
     self->bitmask = (1 << bits_per_value) - 1;
+
+    self->dirty_area.x1 = 0;
+    self->dirty_area.x2 = width;
+    self->dirty_area.y1 = 0;
+    self->dirty_area.y2 = height;
 }
 
 uint16_t common_hal_displayio_bitmap_get_height(displayio_bitmap_t *self) {
@@ -104,6 +109,26 @@ void common_hal_displayio_bitmap_set_pixel(displayio_bitmap_t *self, int16_t x,
     if (self->read_only) {
         mp_raise_RuntimeError(translate("Read-only object"));
     }
+    // Update the dirty area.
+    if (self->dirty_area.x1 == self->dirty_area.x2) {
+        self->dirty_area.x1 = x;
+        self->dirty_area.x2 = x + 1;
+        self->dirty_area.y1 = y;
+        self->dirty_area.y2 = y + 1;
+    } else {
+        if (x < self->dirty_area.x1) {
+            self->dirty_area.x1 = x;
+        } else if (x >= self->dirty_area.x2) {
+            self->dirty_area.x2 = x + 1;
+        }
+        if (y < self->dirty_area.y1) {
+            self->dirty_area.y1 = y;
+        } else if (y >= self->dirty_area.y2) {
+            self->dirty_area.y2 = y + 1;
+        }
+    }
+
+    // Update our data
     int32_t row_start = y * self->stride;
     uint32_t bytes_per_value = self->bits_per_value / 8;
     if (bytes_per_value < 1) {
@@ -124,3 +149,16 @@ void common_hal_displayio_bitmap_set_pixel(displayio_bitmap_t *self, int16_t x,
         }
     }
 }
+
+displayio_area_t* displayio_bitmap_get_refresh_areas(displayio_bitmap_t *self, displayio_area_t* tail) {
+    if (self->dirty_area.x1 == self->dirty_area.x2) {
+        return tail;
+    }
+    self->dirty_area.next = tail;
+    return &self->dirty_area;
+}
+
+void displayio_bitmap_finish_refresh(displayio_bitmap_t *self) {
+    self->dirty_area.x1 = 0;
+    self->dirty_area.x2 = 0;
+}