[vtbackend] Implements DSR ?996 to report color palette updates (expl…

…icit and unsolicited) and adds DEC mode 2031 to enable/disable unsolicited reports of that

Signed-off-by: Christian Parpart <[email protected]>

metainfo.xml

@@ -129,6 +129,8 @@
           <li>Removes the ability to inline colorschemes within a configuration profile. Colorschemes must now always be referenced by their name.</li>
           <li>Adds the ability to chose a color scheme based on the operating systems's dark/light mode setting. This will change live whenever the OS's dark/light mode setting changes as well (#604).</li>
           <li>Adds VT sequence DECSSCLS (change scroll speed) and properly handle DECSCLM (enable slow scrolling mode) (#1204)</li>
+          <li>Adds VT sequence parameter ?996 to DSR to request a report of current color scheme dark/light mode hint.</li>
+          <li>Adds VT sequence `SM ?2031` and `RM ?2031` to enable/disable unsolicited DSR for color scheme updates by the user or OS.</li>
           <li>Adds percentage value to Indicator Statusline to indicate scroll offset in scrollback buffer.</li>
           <li>Adds inheritance of profiles in configuration file based on default profile (#1063).</li>
           <li>Adds config option `profile.*.bell` to adjust BEL behavior and fixes (#1162) and (#1163).</li>

src/vtbackend/Screen.cpp

@@ -78,6 +78,9 @@ using std::vector;
 namespace vtbackend
 {
 
+auto constexpr inline ColorPaletteUpdateDsrRequestId = 996;
+auto constexpr inline ColorPaletteUpdateDsrReplyId = 997;
+
 auto constexpr inline TabWidth = ColumnCount(8);
 
 auto const inline vtCaptureBufferLog = logstore::category("vt.ext.capturebuffer",
@@ -92,6 +95,11 @@ auto const inline vtCaptureBufferLog = logstore::category("vt.ext.capturebuffer"
 
 namespace // {{{ helper
 {
+    constexpr bool isLightColor(RGBColor color) noexcept
+    {
+        return ((5 * color.green) + (2 * color.red) + color.blue) > 8 * 128;
+    }
+
     template <typename Rep, typename Period>
     inline void sleep_for(std::chrono::duration<Rep, Period> const& rtime)
     {
@@ -877,6 +885,19 @@ void Screen<Cell>::reportCursorPosition()
     _terminal->reply("\033[{};{}R", logicalCursorPosition().line + 1, logicalCursorPosition().column + 1);
 }
 
+template <typename Cell>
+CRISPY_REQUIRES(CellConcept<Cell>)
+void Screen<Cell>::reportColorPaletteUpdate()
+{
+    auto constexpr DarkModeHint = 1;
+    auto constexpr LightModeHint = 2;
+
+    auto const modeHint = isLightColor(_state->colorPalette.defaultForeground) ? DarkModeHint : LightModeHint;
+
+    _terminal->reply("\033[?{};{}n", ColorPaletteUpdateDsrReplyId, modeHint);
+    _terminal->flushInput();
+}
+
 template <typename Cell>
 CRISPY_REQUIRES(CellConcept<Cell>)
 void Screen<Cell>::reportExtendedCursorPosition()
@@ -2800,6 +2821,9 @@ namespace impl
         {
             switch (seq.param(0))
             {
+                case ColorPaletteUpdateDsrRequestId:
+                    screen.reportColorPaletteUpdate();
+                    return ApplyResult::Ok;
                 default: return ApplyResult::Unsupported;
             }
         }

src/vtbackend/Screen.h

@@ -50,6 +50,7 @@ class ScreenBase: public SequenceHandler
     void resetSavedCursorState() { _savedCursor = {}; }
     virtual void saveCursor() = 0;
     virtual void restoreCursor() = 0;
+    virtual void reportColorPaletteUpdate() = 0;
 
     [[nodiscard]] virtual Margin margin() const noexcept = 0;
     [[nodiscard]] virtual Margin& margin() noexcept = 0;
@@ -220,6 +221,7 @@ class Screen final: public ScreenBase, public capabilities::StaticDatabase
     void deviceStatusReport();           // DSR
     void reportCursorPosition();         // CPR
     void reportExtendedCursorPosition(); // DECXCPR
+    void reportColorPaletteUpdate() override;
     void selectConformanceLevel(VTType level);
     void requestDynamicColor(DynamicColorName name);
     void requestCapability(capabilities::Code code);

src/vtbackend/Terminal.cpp

@@ -2195,6 +2195,9 @@ void Terminal::resetColorPalette(ColorPalette const& colors)
     _state.defaultColorPalette = colors;
     _settings.colorPalette = colors;
     _factorySettings.colorPalette = colors;
+
+    if (isModeEnabled(DECMode::ReportColorPaletteUpdated))
+        _currentScreen.get().reportColorPaletteUpdate();
 }
 
 void Terminal::pushColorPalette(size_t slot)

src/vtbackend/TerminalState.cpp

@@ -81,6 +81,7 @@ std::string to_string(DECMode mode)
         case DECMode::Unicode: return "Unicode";
         case DECMode::TextReflow: return "TextReflow";
         case DECMode::SixelCursorNextToGraphic: return "SixelCursorNextToGraphic";
+        case DECMode::ReportColorPaletteUpdated: return "ReportColorPaletteUpdated";
     }
     return fmt::format("({})", static_cast<unsigned>(mode));
 }

src/vtbackend/primitives.h

@@ -686,6 +686,10 @@ enum class DECMode
     // intersecting with the main page area.
     ReportGridCellSelection = 2030,
 
+    // If enabled, the terminal will report color palette changes to the application,
+    // if modified by the user or operating system (e.g. dark/light mode adaption).
+    ReportColorPaletteUpdated = 2031,
+
     // If enabled (default, as per spec), then the cursor is left next to the graphic,
     // that is, the text cursor is placed at the position of the sixel cursor.
     // If disabled otherwise, the cursor is placed below the image, as if CR LF was sent,
@@ -791,6 +795,7 @@ constexpr unsigned toDECModeNum(DECMode m)
         case DECMode::MouseAlternateScroll: return 1007;
         case DECMode::MousePassiveTracking: return 2029;
         case DECMode::ReportGridCellSelection: return 2030;
+        case DECMode::ReportColorPaletteUpdated: return 2031;
         case DECMode::BatchedRendering: return 2026;
         case DECMode::Unicode: return 2027;
         case DECMode::TextReflow: return 2028;
@@ -837,6 +842,7 @@ constexpr bool isValidDECMode(unsigned int mode) noexcept
         case DECMode::MouseAlternateScroll:
         case DECMode::MousePassiveTracking:
         case DECMode::ReportGridCellSelection:
+        case DECMode::ReportColorPaletteUpdated:
         case DECMode::BatchedRendering:
         case DECMode::Unicode:
         case DECMode::TextReflow: