[st7735][st7789v][st7920] Fix display buffer overflows and dead code (#14511)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

esphome/components/st7735/st7735.cpp

@@ -466,7 +466,7 @@ void HOT ST7735::write_display_data_() {
 }
 
 void ST7735::spi_master_write_addr_(uint16_t addr1, uint16_t addr2) {
-  static uint8_t byte[4];
+  uint8_t byte[4];
   byte[0] = (addr1 >> 8) & 0xFF;
   byte[1] = addr1 & 0xFF;
   byte[2] = (addr2 >> 8) & 0xFF;
@@ -476,17 +476,5 @@ void ST7735::spi_master_write_addr_(uint16_t addr1, uint16_t addr2) {
   this->write_array(byte, 4);
 }
 
-void ST7735::spi_master_write_color_(uint16_t color, uint16_t size) {
-  static uint8_t byte[1024];
-  int index = 0;
-  for (int i = 0; i < size; i++) {
-    byte[index++] = (color >> 8) & 0xFF;
-    byte[index++] = color & 0xFF;
-  }
-
-  this->dc_pin_->digital_write(true);
-  write_array(byte, size * 2);
-}
-
 }  // namespace st7735
 }  // namespace esphome

esphome/components/st7735/st7735.h

@@ -68,7 +68,6 @@ class ST7735 : public display::DisplayBuffer,
   void set_addr_window_(uint16_t x, uint16_t y, uint16_t w, uint16_t h);
   void draw_absolute_pixel_internal(int x, int y, Color color) override;
   void spi_master_write_addr_(uint16_t addr1, uint16_t addr2);
-  void spi_master_write_color_(uint16_t color, uint16_t size);
 
   int get_width_internal() override;
   int get_height_internal() override;

esphome/components/st7789v/st7789v.cpp

@@ -1,11 +1,16 @@
 #include "st7789v.h"
 #include "esphome/core/log.h"
+#include <algorithm>
 
 namespace esphome {
 namespace st7789v {
 
 static const char *const TAG = "st7789v";
-static const size_t TEMP_BUFFER_SIZE = 128;
+#ifdef USE_ESP32
+static constexpr size_t TEMP_BUFFER_SIZE = 1024;
+#else
+static constexpr size_t TEMP_BUFFER_SIZE = 512;
+#endif
 
 void ST7789V::setup() {
 #ifdef USE_POWER_SUPPLY
@@ -236,7 +241,7 @@ void ST7789V::write_data_(uint8_t value) {
 }
 
 void ST7789V::write_addr_(uint16_t addr1, uint16_t addr2) {
-  static uint8_t byte[4];
+  uint8_t byte[4];
   byte[0] = (addr1 >> 8) & 0xFF;
   byte[1] = addr1 & 0xFF;
   byte[2] = (addr2 >> 8) & 0xFF;
@@ -247,15 +252,19 @@ void ST7789V::write_addr_(uint16_t addr1, uint16_t addr2) {
 }
 
 void ST7789V::write_color_(uint16_t color, uint16_t size) {
-  static uint8_t byte[1024];
-  int index = 0;
-  for (int i = 0; i < size; i++) {
-    byte[index++] = (color >> 8) & 0xFF;
-    byte[index++] = color & 0xFF;
-  }
-
+  uint8_t byte[TEMP_BUFFER_SIZE];
+  uint16_t remaining = size;
   this->dc_pin_->digital_write(true);
-  write_array(byte, size * 2);
+  while (remaining > 0) {
+    uint16_t batch = std::min(remaining, static_cast<uint16_t>(sizeof(byte) / 2));
+    int index = 0;
+    for (int i = 0; i < batch; i++) {
+      byte[index++] = (color >> 8) & 0xFF;
+      byte[index++] = color & 0xFF;
+    }
+    this->write_array(byte, batch * 2);
+    remaining -= batch;
+  }
 }
 
 size_t ST7789V::get_buffer_length_() {

esphome/components/st7920/st7920.cpp

@@ -72,16 +72,19 @@ void ST7920::goto_xy_(uint16_t x, uint16_t y) {
 }
 
 void HOT ST7920::write_display_data() {
-  uint8_t i, j, b;
-  for (j = 0; j < (uint8_t) (this->get_height_internal() / 2); j++) {
+  int i, j;
+  uint8_t b;
+  int width_bytes = this->get_width_internal() / 8;
+  int half_height = this->get_height_internal() / 2;
+  for (j = 0; j < half_height; j++) {
     this->goto_xy_(0, j);
     this->enable();
-    for (i = 0; i < 16; i++) {  // 16 bytes from line #0+
-      b = this->buffer_[i + j * 16];
+    for (i = 0; i < width_bytes; i++) {
+      b = this->buffer_[i + j * width_bytes];
       this->send_(LCD_DATA, b);
     }
-    for (i = 0; i < 16; i++) {  // 16 bytes from line #32+
-      b = this->buffer_[i + (j + 32) * 16];
+    for (i = 0; i < width_bytes; i++) {
+      b = this->buffer_[i + (j + half_height) * width_bytes];
       this->send_(LCD_DATA, b);
     }
     this->disable();