Fix large blacklevel step. Lower 25% of shades are now accessible.

There is a large step in brightness from level zero to level one.
After experimenting with various ST7789 options, I found that
decreasing VDV to 0x10 (-0.4V) fixes this issue.

The gamma change reduced the average error in brightness, but with the
underlying issue fixed, the gamma change has been reverted.

src/displayapp/screens/HeartRate.cpp

@@ -49,7 +49,7 @@ HeartRate::HeartRate(Pinetime::Applications::DisplayApp* app,
   lv_obj_align(label_bpm, label_hr, LV_ALIGN_OUT_TOP_MID, 0, -20);
 
   label_status = lv_label_create(lv_scr_act(), nullptr);
-  lv_obj_set_style_local_text_color(label_status, LV_LABEL_PART_MAIN, LV_STATE_DEFAULT, lv_color_hex(0x222222));
+  lv_obj_set_style_local_text_color(label_status, LV_LABEL_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_GRAY);
   lv_label_set_text_static(label_status, ToString(Pinetime::Controllers::HeartRateController::States::NotEnoughData));
 
   lv_obj_align(label_status, label_hr, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);

src/displayapp/screens/List.cpp

@@ -67,7 +67,7 @@ List::List(uint8_t screenID,
     if (applications[i].application != Apps::None) {
 
       itemApps[i] = lv_btn_create(container1, nullptr);
-      lv_obj_set_style_local_bg_opa(itemApps[i], LV_BTN_PART_MAIN, LV_STATE_DEFAULT, LV_OPA_40);
+      lv_obj_set_style_local_bg_opa(itemApps[i], LV_BTN_PART_MAIN, LV_STATE_DEFAULT, LV_OPA_50);
       lv_obj_set_style_local_radius(itemApps[i], LV_BTN_PART_MAIN, LV_STATE_DEFAULT, 57);
       lv_obj_set_style_local_bg_color(itemApps[i], LV_BTN_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_AQUA);
 

src/displayapp/screens/Music.cpp

@@ -53,7 +53,7 @@ Music::Music(Pinetime::Applications::DisplayApp* app, Pinetime::Controllers::Mus
   lv_style_init(&btn_style);
   lv_style_set_radius(&btn_style, LV_STATE_DEFAULT, 20);
   lv_style_set_bg_color(&btn_style, LV_STATE_DEFAULT, LV_COLOR_AQUA);
-  lv_style_set_bg_opa(&btn_style, LV_STATE_DEFAULT, LV_OPA_40);
+  lv_style_set_bg_opa(&btn_style, LV_STATE_DEFAULT, LV_OPA_50);
 
   btnVolDown = lv_btn_create(lv_scr_act(), nullptr);
   btnVolDown->user_data = this;

src/displayapp/screens/Notifications.cpp

@@ -181,7 +181,7 @@ Notifications::NotificationItem::NotificationItem(const char* title,
   : mode {mode}, alertNotificationService {alertNotificationService}, motorController {motorController} {
   lv_obj_t* container1 = lv_cont_create(lv_scr_act(), NULL);
 
-  lv_obj_set_style_local_bg_color(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_MAKE(0x30, 0x30, 0x30));
+  lv_obj_set_style_local_bg_color(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_MAKE(0x38, 0x38, 0x38));
   lv_obj_set_style_local_pad_all(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 10);
   lv_obj_set_style_local_pad_inner(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 5);
   lv_obj_set_style_local_border_width(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 0);

src/displayapp/screens/StopWatch.cpp

@@ -65,7 +65,7 @@ StopWatch::StopWatch(DisplayApp* app, System::SystemTask& systemTask)
   lv_obj_set_event_cb(btnStopLap, stop_lap_event_handler);
   lv_obj_set_size(btnStopLap, 115, 50);
   lv_obj_align(btnStopLap, lv_scr_act(), LV_ALIGN_IN_BOTTOM_LEFT, 0, 0);
-  lv_obj_set_style_local_bg_color(btnStopLap, LV_BTN_PART_MAIN, LV_STATE_DISABLED, lv_color_hex(0x0b0b0b));
+  lv_obj_set_style_local_bg_color(btnStopLap, LV_BTN_PART_MAIN, LV_STATE_DISABLED, LV_COLOR_MAKE(0x18, 0x18, 0x18));
   txtStopLap = lv_label_create(btnStopLap, nullptr);
   lv_obj_set_style_local_text_color(txtStopLap, LV_BTN_PART_MAIN, LV_STATE_DISABLED, LV_COLOR_MAKE(0xb0, 0xb0, 0xb0));
   lv_label_set_text_static(txtStopLap, Symbols::stop);

src/displayapp/screens/Tile.cpp

@@ -87,9 +87,9 @@ Tile::Tile(uint8_t screenID,
   lv_obj_align(btnm1, NULL, LV_ALIGN_CENTER, 0, 10);
 
   lv_obj_set_style_local_radius(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DEFAULT, 20);
-  lv_obj_set_style_local_bg_opa(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DEFAULT, LV_OPA_40);
+  lv_obj_set_style_local_bg_opa(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DEFAULT, LV_OPA_50);
   lv_obj_set_style_local_bg_color(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DEFAULT, LV_COLOR_AQUA);
-  lv_obj_set_style_local_bg_opa(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DISABLED, LV_OPA_40);
+  lv_obj_set_style_local_bg_opa(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DISABLED, LV_OPA_50);
   lv_obj_set_style_local_bg_color(btnm1, LV_BTNMATRIX_PART_BTN, LV_STATE_DISABLED, lv_color_hex(0x111111));
   lv_obj_set_style_local_pad_all(btnm1, LV_BTNMATRIX_PART_BG, LV_STATE_DEFAULT, 0);
   lv_obj_set_style_local_pad_inner(btnm1, LV_BTNMATRIX_PART_BG, LV_STATE_DEFAULT, 10);

src/displayapp/screens/settings/QuickSettings.cpp

@@ -49,7 +49,7 @@ QuickSettings::QuickSettings(Pinetime::Applications::DisplayApp* app,
 
   lv_style_init(&btn_style);
   lv_style_set_radius(&btn_style, LV_STATE_DEFAULT, buttonHeight / 4);
-  lv_style_set_bg_color(&btn_style, LV_STATE_DEFAULT, LV_COLOR_MAKE(0x1c, 0x1c, 0x1c));
+  lv_style_set_bg_color(&btn_style, LV_STATE_DEFAULT, LV_COLOR_MAKE(0x38, 0x38, 0x38));
 
   btn1 = lv_btn_create(lv_scr_act(), nullptr);
   btn1->user_data = this;

src/drivers/St7789.cpp

@@ -23,7 +23,7 @@ void St7789::Init() {
   RowAddressSet();
   DisplayInversionOn();
   NormalModeOn();
-  SetGamma();
+  SetVdv();
   DisplayOn();
 }
 
@@ -115,9 +115,11 @@ void St7789::WriteToRam() {
   WriteCommand(static_cast<uint8_t>(Commands::WriteToRam));
 }
 
-void St7789::SetGamma() {
+void St7789::SetVdv() {
-  WriteCommand(static_cast<uint8_t>(Commands::GammaSet));
+  // By default there is a large step from pixel brightness zero to one.
-  WriteData(0x04);
+  // After experimenting with VCOMS, VRH and VDV, this was found to produce good results.
+  WriteCommand(static_cast<uint8_t>(Commands::VdvSet));
+  WriteData(0x10);
 }
 
 void St7789::DisplayOff() {

src/drivers/St7789.h

@@ -43,7 +43,7 @@ namespace Pinetime {
       void NormalModeOn();
       void WriteToRam();
       void SetAddrWindow(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1);
-      void SetGamma();
+      void SetVdv();
       void WriteCommand(uint8_t cmd);
       void WriteSpi(const uint8_t* data, size_t size);
 
@@ -53,7 +53,6 @@ namespace Pinetime {
         SleepOut = 0x11,
         NormalModeOn = 0x13,
         DisplayInversionOn = 0x21,
-        GammaSet = 0x26,
         DisplayOff = 0x28,
         DisplayOn = 0x29,
         ColumnAddressSet = 0x2a,
@@ -63,6 +62,7 @@ namespace Pinetime {
         VerticalScrollDefinition = 0x33,
         VerticalScrollStartAddress = 0x37,
         ColMod = 0x3a,
+        VdvSet = 0xc4,
       };
       void WriteData(uint8_t data);
       void ColumnAddressSet();