Add partial display update support.

Different operations to the display tree have different costs. Be
aware of these costs when optimizing your code.
* Changing tiles indices in a TileGrid will update an area
covering them all.
* Changing a palette will refresh every object that references it.
* Moving a TileGrid will update both where it was and where it moved to.
* Adding something to a Group will refresh each individual area it
covers.
* Removing things from a Group will refresh one area that covers all
previous locations. (Not separate areas like add.)
* Setting a new top level Group will refresh the entire display.

Only TileGrid moves are optimized for overlap. All other overlaps
cause sending of duplicate pixels.

This also adds flip_x, flip_y and transpose_xy to TileGrid. They
change the direction of the pixels but not the location.

Fixes #1169. Fixes #1705. Fixes #1923.

1 files changed, 19 insertions, 3 deletions

diff --git a/shared-module/displayio/area.h b/shared-module/displayio/area.h
index 9db57e13f..ec7c389b4 100644
--- a/shared-module/displayio/area.h
+++ b/shared-module/displayio/area.h
@@ -28,23 +28,35 @@
 #define MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_AREA_H
 
 // Implementations are in __init__.c
+typedef struct _displayio_area_t displayio_area_t;
 
-typedef struct {
+struct _displayio_area_t {
     int16_t x1;
     int16_t y1;
     int16_t x2; // Second point is exclusive.
     int16_t y2;
-} displayio_area_t;
+    const displayio_area_t* next; // Next area in the linked list.
+};
 
 typedef struct {
+    uint16_t x;
+    uint16_t y;
+    int8_t dx;
+    int8_t dy;
+    uint8_t scale;
     uint16_t width;
     uint16_t height;
-    uint8_t scale;
     bool mirror_x;
     bool mirror_y;
     bool transpose_xy;
 } displayio_buffer_transform_t;
 
+void displayio_area_union(const displayio_area_t* a,
+                          const displayio_area_t* b,
+                          displayio_area_t* u);
+void displayio_area_expand(displayio_area_t* original, const displayio_area_t* addition);
+void displayio_area_copy(const displayio_area_t* src, displayio_area_t* dst);
+void displayio_area_scale(displayio_area_t* area, uint16_t scale);
 void displayio_area_shift(displayio_area_t* area, int16_t dx, int16_t dy);
 bool displayio_area_compute_overlap(const displayio_area_t* a,
                                     const displayio_area_t* b,
@@ -53,5 +65,9 @@ uint16_t displayio_area_width(const displayio_area_t* area);
 uint16_t displayio_area_height(const displayio_area_t* area);
 uint32_t displayio_area_size(const displayio_area_t* area);
 bool displayio_area_equal(const displayio_area_t* a, const displayio_area_t* b);
+void displayio_area_transform_within(bool mirror_x, bool mirror_y, bool transpose_xy,
+                                     const displayio_area_t* original,
+                                     const displayio_area_t* whole,
+                                     displayio_area_t* transformed);
 
 #endif // MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_AREA_H