displayio: make region command sends reusable for QSPI transactions

Refactor display bus region-update command emission into a shared helper with
optional transaction management. Keep the existing public path unchanged, and
add a QSPIBus-only entrypoint that can send region commands without nesting
begin/end transaction calls.

Also remove the TileGrid 16bpp+Palette fast path so fill_area uses the generic
path, and fix indentation in QSPIBus write_data.

Author: ppsx

ports/espressif/common-hal/qspibus/QSPIBus.c

@@ -464,7 +464,7 @@ void common_hal_qspibus_qspibus_write_data(
         }
         return;
     }
-   if (!self->has_pending_command) {
+    if (!self->has_pending_command) {
         mp_raise_ValueError(MP_ERROR_TEXT("No pending command"));
     }
 

shared-module/displayio/TileGrid.c

@@ -512,75 +512,6 @@ bool displayio_tilegrid_fill_area(displayio_tilegrid_t *self,
         y_shift = temp_shift;
     }
 
-    // Fast path for the common case: single-tile, 16bpp bitmap with Palette,
-    // no transforms, full coverage.  Inlines bitmap access and palette cache
-    // lookup to eliminate per-pixel function-call overhead (~4-5x speedup).
-    if (full_coverage &&
-        colorspace->depth == 16 &&
-        self->width_in_tiles == 1 &&
-        self->height_in_tiles == 1 &&
-        self->absolute_transform->scale == 1 &&
-        self->absolute_transform->dx == 1 &&
-        self->absolute_transform->dy == 1 &&
-        !self->absolute_transform->transpose_xy &&
-        !self->flip_x && !self->flip_y &&
-        !self->transpose_xy &&
-        x_stride == 1 && y_stride == displayio_area_width(area) &&
-        x_shift == 0 && y_shift == 0 &&
-        mp_obj_is_type(self->bitmap, &displayio_bitmap_type) &&
-        mp_obj_is_type(self->pixel_shader, &displayio_palette_type)) {
-
-        displayio_bitmap_t *bmp = MP_OBJ_TO_PTR(self->bitmap);
-        displayio_palette_t *pal = MP_OBJ_TO_PTR(self->pixel_shader);
-
-        if (bmp->bits_per_value == 16 && !pal->dither) {
-            uint16_t *out = (uint16_t *)buffer;
-            bool all_opaque = true;
-
-            // Process all pixels with inlined bitmap access and palette cache.
-            uint32_t idx = 0;
-            for (int16_t y = start_y; y < end_y; ++y) {
-                // Direct row pointer into bitmap data (16bpp → uint16_t).
-                // stride is in uint32_t units, so multiply by 2 for uint16_t indexing.
-                const uint16_t *bmp_row = ((const uint16_t *)bmp->data) + y * (bmp->stride * 2);
-
-                for (int16_t x = start_x; x < end_x; ++x) {
-                    uint16_t px_index = bmp_row[x];
-
-                    // Inline palette cache check (avoids function call overhead).
-                    if (px_index < pal->color_count) {
-                        _displayio_color_t *color = &pal->colors[px_index];
-                        if (color->transparent) {
-                            all_opaque = false;
-                            idx++;
-                            continue;
-                        }
-                        if (color->cached_colorspace == colorspace &&
-                            color->cached_colorspace_grayscale_bit == colorspace->grayscale_bit &&
-                            color->cached_colorspace_grayscale == colorspace->grayscale) {
-                            out[idx] = (uint16_t)color->cached_color;
-                        } else {
-                            // Cache miss — do full conversion, then cache.
-                            displayio_input_pixel_t in_px = {.pixel = px_index};
-                            displayio_output_pixel_t out_px = {.opaque = true};
-                            displayio_palette_get_color(pal, colorspace, &in_px, &out_px);
-                            out[idx] = (uint16_t)out_px.pixel;
-                        }
-                    } else {
-                        // Out of palette range — transparent.
-                        all_opaque = false;
-                        idx++;
-                        continue;
-                    }
-                    mask[idx >> 5] |= 1u << (idx & 31);
-                    idx++;
-                }
-            }
-
-            return all_opaque;
-        }
-    }
-
     displayio_input_pixel_t input_pixel;
     displayio_output_pixel_t output_pixel;
 

shared-module/displayio/bus_core.c

@@ -114,7 +114,7 @@ void displayio_display_bus_end_transaction(displayio_display_bus_t *self) {
     self->end_transaction(self->bus);
 }
 
-void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, displayio_display_core_t *display, displayio_area_t *area) {
+static void _displayio_display_bus_send_region_commands(displayio_display_bus_t *self, displayio_display_core_t *display, displayio_area_t *area, bool manage_transactions) {
     uint16_t x1 = area->x1 + self->colstart;
     uint16_t x2 = area->x2 + self->colstart;
     uint16_t y1 = area->y1 + self->rowstart;
@@ -141,7 +141,9 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
     }
 
     // Set column.
-    displayio_display_bus_begin_transaction(self);
+    if (manage_transactions) {
+        displayio_display_bus_begin_transaction(self);
+    }
     uint8_t data[5];
     data[0] = self->column_command;
     uint8_t data_length = 1;
@@ -176,20 +178,28 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
     }
 
     self->send(self->bus, data_type, chip_select, data, data_length);
-    displayio_display_bus_end_transaction(self);
+    if (manage_transactions) {
+        displayio_display_bus_end_transaction(self);
+    }
 
     if (self->set_current_column_command != NO_COMMAND) {
         uint8_t command = self->set_current_column_command;
-        displayio_display_bus_begin_transaction(self);
+        if (manage_transactions) {
+            displayio_display_bus_begin_transaction(self);
+        }
         self->send(self->bus, DISPLAY_COMMAND, chip_select, &command, 1);
         // Only send the first half of data because it is the first coordinate.
         self->send(self->bus, DISPLAY_DATA, chip_select, data, data_length / 2);
-        displayio_display_bus_end_transaction(self);
+        if (manage_transactions) {
+            displayio_display_bus_end_transaction(self);
+        }
     }
 
 
     // Set row.
-    displayio_display_bus_begin_transaction(self);
+    if (manage_transactions) {
+        displayio_display_bus_begin_transaction(self);
+    }
     data[0] = self->row_command;
     data_length = 1;
     if (!self->data_as_commands) {
@@ -220,18 +230,34 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
     }
 
     self->send(self->bus, data_type, chip_select, data, data_length);
-    displayio_display_bus_end_transaction(self);
+    if (manage_transactions) {
+        displayio_display_bus_end_transaction(self);
+    }
 
     if (self->set_current_row_command != NO_COMMAND) {
         uint8_t command = self->set_current_row_command;
-        displayio_display_bus_begin_transaction(self);
+        if (manage_transactions) {
+            displayio_display_bus_begin_transaction(self);
+        }
         self->send(self->bus, DISPLAY_COMMAND, chip_select, &command, 1);
         // Only send the first half of data because it is the first coordinate.
         self->send(self->bus, DISPLAY_DATA, chip_select, data, data_length / 2);
-        displayio_display_bus_end_transaction(self);
+        if (manage_transactions) {
+            displayio_display_bus_end_transaction(self);
+        }
     }
 }
 
+void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, displayio_display_core_t *display, displayio_area_t *area) {
+    _displayio_display_bus_send_region_commands(self, display, area, true);
+}
+
+#if CIRCUITPY_QSPIBUS
+void displayio_display_bus_send_region_commands(displayio_display_bus_t *self, displayio_display_core_t *display, displayio_area_t *area) {
+    _displayio_display_bus_send_region_commands(self, display, area, false);
+}
+#endif
+
 void displayio_display_bus_collect_ptrs(displayio_display_bus_t *self) {
     self->collect_ptrs(self->bus);
 }