Merge pull request #4331 from dhalbert/tilegrid-transpose-fix

Tilegrid transpose fix

1 files changed, 25 insertions, 10 deletions

diff --git a/shared-module/displayio/TileGrid.c b/shared-module/displayio/TileGrid.c
index 2cd3a4948..96473d4a8 100644
--- a/shared-module/displayio/TileGrid.c
+++ b/shared-module/displayio/TileGrid.c
@@ -74,6 +74,7 @@ void common_hal_displayio_tilegrid_construct(displayio_tilegrid_t *self, mp_obj_
     self->flip_x = false;
     self->flip_y = false;
     self->transpose_xy = false;
+    self->absolute_transform = NULL;
 }
 
 
@@ -110,17 +111,24 @@ void _update_current_x(displayio_tilegrid_t *self) {
     } else {
         width = self->pixel_width;
     }
-    if (self->absolute_transform->transpose_xy) {
-        self->current_area.y1 = self->absolute_transform->y + self->absolute_transform->dy * self->x;
-        self->current_area.y2 = self->absolute_transform->y + self->absolute_transform->dy * (self->x + width);
+
+    // If there's no transform, substitute an identity transform so the calculations will work.
+    const displayio_buffer_transform_t* absolute_transform =
+        self->absolute_transform  == NULL
+        ? &null_transform
+        : self->absolute_transform;
+
+    if (absolute_transform->transpose_xy) {
+        self->current_area.y1 = absolute_transform->y + absolute_transform->dy * self->x;
+        self->current_area.y2 = absolute_transform->y + absolute_transform->dy * (self->x + width);
         if (self->current_area.y2 < self->current_area.y1) {
             int16_t temp = self->current_area.y2;
             self->current_area.y2 = self->current_area.y1;
             self->current_area.y1 = temp;
         }
     } else {
-        self->current_area.x1 = self->absolute_transform->x + self->absolute_transform->dx * self->x;
-        self->current_area.x2 = self->absolute_transform->x + self->absolute_transform->dx * (self->x + width);
+        self->current_area.x1 = absolute_transform->x + absolute_transform->dx * self->x;
+        self->current_area.x2 = absolute_transform->x + absolute_transform->dx * (self->x + width);
         if (self->current_area.x2 < self->current_area.x1) {
             int16_t temp = self->current_area.x2;
             self->current_area.x2 = self->current_area.x1;
@@ -136,17 +144,24 @@ void _update_current_y(displayio_tilegrid_t *self) {
     } else {
         height = self->pixel_height;
     }
-    if (self->absolute_transform->transpose_xy) {
-        self->current_area.x1 = self->absolute_transform->x + self->absolute_transform->dx * self->y;
-        self->current_area.x2 = self->absolute_transform->x + self->absolute_transform->dx * (self->y + height);
+
+    // If there's no transform, substitute an identity transform so the calculations will work.
+    const displayio_buffer_transform_t* absolute_transform =
+        self->absolute_transform  == NULL
+        ? &null_transform
+        : self->absolute_transform;
+
+    if (absolute_transform->transpose_xy) {
+        self->current_area.x1 = absolute_transform->x + absolute_transform->dx * self->y;
+        self->current_area.x2 = absolute_transform->x + absolute_transform->dx * (self->y + height);
         if (self->current_area.x2 < self->current_area.x1) {
             int16_t temp = self->current_area.x2;
             self->current_area.x2 = self->current_area.x1;
             self->current_area.x1 = temp;
         }
     } else {
-        self->current_area.y1 = self->absolute_transform->y + self->absolute_transform->dy * self->y;
-        self->current_area.y2 = self->absolute_transform->y + self->absolute_transform->dy * (self->y + height);
+        self->current_area.y1 = absolute_transform->y + absolute_transform->dy * self->y;
+        self->current_area.y2 = absolute_transform->y + absolute_transform->dy * (self->y + height);
         if (self->current_area.y2 < self->current_area.y1) {
             int16_t temp = self->current_area.y2;
             self->current_area.y2 = self->current_area.y1;