Add persistent OLED UI settings and recovery

src/local_display.c

@@ -7,6 +7,7 @@
 
 #include "board_pins.h"
 #include "driver/i2c_master.h"
+#include "esp_timer.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/semphr.h"
 #include "freertos/task.h"
@@ -21,6 +22,7 @@
 #define LOCAL_DISPLAY_DEFAULT_CONTRAST 127U
 #define LOCAL_DISPLAY_COMMAND_CAPACITY 32U
 #define LOCAL_DISPLAY_DATA_CHUNK_SIZE 128U
+#define LOCAL_DISPLAY_FLUSH_BUDGET_US (500LL * 1000LL)
 
 static const uint8_t s_expected_addresses[] = {0x3cU, 0x3dU};
 
@@ -172,6 +174,7 @@ static esp_err_t flush_dirty_locked(void)
         return ESP_ERR_INVALID_STATE;
     }
 
+    int64_t started = esp_timer_get_time();
     uint8_t transfer[LOCAL_DISPLAY_DATA_CHUNK_SIZE + 1U];
     transfer[0] = 0x40U;
     for (uint8_t page = 0U; page < LOCAL_DISPLAY_PAGE_COUNT; ++page) {
@@ -179,6 +182,9 @@ static esp_err_t flush_dirty_locked(void)
         if ((s_dirty_pages & page_mask) == 0U) {
             continue;
         }
+        if ((esp_timer_get_time() - started) >= LOCAL_DISPLAY_FLUSH_BUDGET_US) {
+            return ESP_ERR_TIMEOUT;
+        }
 
         const uint8_t commands[] = {
             0x21U, 0x00U, (uint8_t)(LOCAL_DISPLAY_WIDTH - 1U),
@@ -188,6 +194,9 @@ static esp_err_t flush_dirty_locked(void)
         if (error != ESP_OK) {
             return error;
         }
+        if ((esp_timer_get_time() - started) >= LOCAL_DISPLAY_FLUSH_BUDGET_US) {
+            return ESP_ERR_TIMEOUT;
+        }
         memcpy(&transfer[1], &s_framebuffer[(size_t)page * LOCAL_DISPLAY_WIDTH],
                LOCAL_DISPLAY_WIDTH);
         error = i2c_master_transmit(s_device, transfer, sizeof(transfer),