displayio: Move bitmap read-only checking to displayio_bitmap_set_dirty_area

This is a modest code savings, but more importantly it reduces
boilerplate in bitmap-modifying routines.

Callers need only ensure they call displayio_bitmap_set_dirty_area in
advance of the bitmap modifications they perform.

(note that this assumes that no bitmap operation can enter background
tasks. If an operation COULD enter background tasks, it MUST re-dirty
the area it touches when it exits, simply by a fresh call to
set_dirty_area with the same area as before)

Author: jepler

shared-module/bitmaptools/__init__.c

@@ -95,10 +95,6 @@ void common_hal_bitmaptools_rotozoom(displayio_bitmap_t *self, int16_t ox, int16
     // #    */
 
 
-    if (self->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-
     int16_t x,y;
 
     int16_t minx = dest_clip1_x;
@@ -199,6 +195,9 @@ void common_hal_bitmaptools_rotozoom(displayio_bitmap_t *self, int16_t ox, int16
     float rowu = startu + miny * duCol;
     float rowv = startv + miny * dvCol;
 
+    displayio_area_t dirty_area = {minx, miny, maxx, maxy};
+    displayio_bitmap_set_dirty_area(self, &dirty_area);
+
     for (y = miny; y <= maxy; y++) {
         float u = rowu + minx * duRow;
         float v = rowv + minx * dvRow;
@@ -236,10 +235,6 @@ void common_hal_bitmaptools_fill_region(displayio_bitmap_t *destination,
     //
     // input checks should ensure that x1 < x2 and y1 < y2 and are within the bitmap region
 
-    if (destination->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-
     displayio_area_t area = { x1, y1, x2, y2 };
     displayio_area_canon(&area);
 
@@ -262,10 +257,6 @@ void common_hal_bitmaptools_draw_line(displayio_bitmap_t *destination,
     int16_t x1, int16_t y1,
     uint32_t value) {
 
-    if (destination->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-
     //
     // adapted from Adafruit_CircuitPython_Display_Shapes.Polygon._line
     //
@@ -394,9 +385,8 @@ void common_hal_bitmaptools_arrayblit(displayio_bitmap_t *self, void *data, int
 void common_hal_bitmaptools_readinto(displayio_bitmap_t *self, pyb_file_obj_t *file, int element_size, int bits_per_pixel, bool reverse_pixels_in_element, bool swap_bytes) {
     uint32_t mask = (1 << common_hal_displayio_bitmap_get_bits_per_value(self)) - 1;
 
-    if (self->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
+    displayio_area_t a = {0, 0, self->width, self->height};
+    displayio_bitmap_set_dirty_area(self, &a);
 
     size_t elements_per_row = (self->width * bits_per_pixel + element_size * 8 - 1) / (element_size * 8);
     size_t rowsize = element_size * elements_per_row;
@@ -472,7 +462,4 @@ void common_hal_bitmaptools_readinto(displayio_bitmap_t *self, pyb_file_obj_t *f
             displayio_bitmap_write_pixel(self, x, y, value & mask);
         }
     }
-
-    displayio_area_t a = {0, 0, self->width, self->height};
-    displayio_bitmap_set_dirty_area(self, &a);
 }

shared-module/displayio/Bitmap.c

@@ -106,6 +106,10 @@ uint32_t common_hal_displayio_bitmap_get_pixel(displayio_bitmap_t *self, int16_t
 }
 
 void displayio_bitmap_set_dirty_area(displayio_bitmap_t *self, const displayio_area_t *dirty_area) {
+    if (self->read_only) {
+        mp_raise_RuntimeError(translate("Read-only object"));
+    }
+
     displayio_area_t area = *dirty_area;
     displayio_area_canon(&area);
     displayio_area_union(&area, &self->dirty_area, &area);
@@ -146,10 +150,6 @@ void common_hal_displayio_bitmap_blit(displayio_bitmap_t *self, int16_t x, int16
     // If skip_value is `None`, then all pixels are copied.
     // This function assumes input checks were performed for pixel index entries.
 
-    if (self->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-
     // Update the dirty area
     int16_t dirty_x_max = (x + (x2 - x1));
     if (dirty_x_max > self->width) {
@@ -198,10 +198,6 @@ void common_hal_displayio_bitmap_blit(displayio_bitmap_t *self, int16_t x, int16
 }
 
 void common_hal_displayio_bitmap_set_pixel(displayio_bitmap_t *self, int16_t x, int16_t y, uint32_t value) {
-    if (self->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-
     // update the dirty region
     displayio_area_t a = {x, y, x + 1, y + 1};
     displayio_bitmap_set_dirty_area(self, &a);
@@ -225,14 +221,8 @@ void displayio_bitmap_finish_refresh(displayio_bitmap_t *self) {
 }
 
 void common_hal_displayio_bitmap_fill(displayio_bitmap_t *self, uint32_t value) {
-    if (self->read_only) {
-        mp_raise_RuntimeError(translate("Read-only object"));
-    }
-    // Update the dirty area.
-    self->dirty_area.x1 = 0;
-    self->dirty_area.x2 = self->width;
-    self->dirty_area.y1 = 0;
-    self->dirty_area.y2 = self->height;
+    displayio_area_t a = {0, 0, self->width, self->height};
+    displayio_bitmap_set_dirty_area(self, &a);
 
     // build the packed word
     uint32_t word = 0;