[plasma-mobile/qmlkonsole] /: Properly implement setting background opacity

Git commit aa62eca31b9b7cae94b06ef16a0d7b89cac60bfc by Devin Lin.
Committed on 19/07/2026 at 17:49.
Pushed by devinlin into branch 'master'.

Properly implement setting background opacity

Currently the opacity setting sets the entire terminal opacity, including the foreground text. Fix it so that it only sets the background color opacity.

M  +17   -6    lib/TerminalDisplay.cpp
M  +6    -5    lib/TerminalDisplay.h
M  +1    -1    src/contents/ui/TerminalPage.qml

https://invent.kde.org/plasma-mobile/qmlkonsole/-/commit/aa62eca31b9b7cae94b06ef16a0d7b89cac60bfc

diff --git a/lib/TerminalDisplay.cpp b/lib/TerminalDisplay.cpp
index bc5f260..b9768bf 100644
--- a/lib/TerminalDisplay.cpp
+++ b/lib/TerminalDisplay.cpp
@@ -298,7 +298,7 @@ TerminalDisplay::TerminalDisplay(QQuickItem *parent)
     , _outputSuspendedLabel(nullptr)
     , _lineSpacing(0)
     , _colorsInverted(false)
-    , _opacity(static_cast<qreal>(1))
+    , _backgroundOpacity(static_cast<qreal>(1))
     , _filterChain(std::make_unique<TerminalImageFilterChain>())
     , _cursorShape(Emulation::KeyboardCursorShape::BlockCursor)
     , mMotionAfterPasting(NoMoveScreenWindow)
@@ -362,6 +362,7 @@ TerminalDisplay::TerminalDisplay(QQuickItem *parent)
     // TODO Forcing rendering to Framebuffer. We need to determine if this is ok
     // always or if we need to make this customizable.
     setRenderTarget(QQuickPaintedItem::FramebufferObject);
+    setFillColor(Qt::transparent);
 
     //  setFocusPolicy( Qt::WheelFocus );
 
@@ -641,10 +642,21 @@ QColor TerminalDisplay::keyboardCursorColor() const
     return _cursorColor;
 }
 
-void TerminalDisplay::setOpacity(qreal opacity)
+qreal TerminalDisplay::backgroundOpacity() const
 {
-    _opacity = qBound(static_cast<qreal>(0), opacity, static_cast<qreal>(1));
+    return _backgroundOpacity;
+}
+
+void TerminalDisplay::setBackgroundOpacity(qreal opacity)
+{
+    const qreal boundedOpacity = qBound(static_cast<qreal>(0), opacity, static_cast<qreal>(1));
+    if (qFuzzyCompare(_backgroundOpacity, boundedOpacity)) {
+        return;
+    }
+
+    _backgroundOpacity = boundedOpacity;
     update();
+    Q_EMIT backgroundOpacityChanged();
 }
 
 void TerminalDisplay::drawBackground(QPainter &painter, const QRect &rect, const QColor &backgroundColor, bool useOpacitySetting)
@@ -654,7 +666,7 @@ void TerminalDisplay::drawBackground(QPainter &painter, const QRect &rect, const
     // left to the widget style for a consistent look.
     if (useOpacitySetting) {
         QColor color(backgroundColor);
-        color.setAlphaF(_opacity);
+        color.setAlphaF(color.alphaF() * _backgroundOpacity);
 
         painter.save();
         painter.setCompositionMode(QPainter::CompositionMode_Source);
@@ -1367,7 +1379,7 @@ QRect TerminalDisplay::calculateTextArea(int topLeftX, int topLeftY, int startCo
 
 void TerminalDisplay::drawContents(QPainter &paint, const QRect &rect)
 {
-    // Draw opaque background
+    // Draw background
     drawBackground(paint, contentsRect(), _colorTable[DEFAULT_BACK_COLOR].color, true);
 
     QPoint tL = contentsRect().topLeft();
@@ -2978,7 +2990,6 @@ void TerminalDisplay::setColorScheme(const QString &name)
 
         setColorTable(cs->getColorTable());
 
-        setFillColor(cs->backgroundColor());
         _colorScheme = name;
         Q_EMIT colorSchemeChanged();
     }
diff --git a/lib/TerminalDisplay.h b/lib/TerminalDisplay.h
index 721272a..8448d9c 100644
--- a/lib/TerminalDisplay.h
+++ b/lib/TerminalDisplay.h
@@ -108,7 +108,7 @@ class KONSOLEPRIVATE_EXPORT TerminalDisplay : public QQuickPaintedItem
     Q_PROPERTY(bool blinkingCursor READ blinkingCursor WRITE setBlinkingCursor NOTIFY blinkingCursorStateChanged)
     Q_PROPERTY(bool antialiasText READ antialias WRITE setAntialias)
     Q_PROPERTY(QStringList availableColorSchemes READ availableColorSchemes NOTIFY availableColorSchemesChanged)
-    Q_PROPERTY(qreal backgroundOpacity READ opacity WRITE setOpacity NOTIFY opacityChanged)
+    Q_PROPERTY(qreal backgroundOpacity READ backgroundOpacity WRITE setBackgroundOpacity NOTIFY backgroundOpacityChanged)
 
 public:
     /** Constructs a new terminal display widget with the specified parent. */
@@ -133,8 +133,8 @@ public:
      */
     uint randomSeed() const;
 
-    /** Sets the opacity of the terminal display. */
-    void setOpacity(qreal opacity);
+    qreal backgroundOpacity() const;
+    void setBackgroundOpacity(qreal opacity);
 
     /**
      * This enum describes the location where the scroll bar is positioned in the display widget.
@@ -698,6 +698,7 @@ Q_SIGNALS:
     void fullCursorHeightChanged();
     void blinkingCursorStateChanged();
     void boldIntenseChanged();
+    void backgroundOpacityChanged();
 
 protected:
     bool event(QEvent *) override;
@@ -794,7 +795,7 @@ private:
     void drawTextFragment(QPainter &painter, const QRect &rect, const QString &text, const Character *style);
     // draws the background for a text fragment
     // if useOpacitySetting is true then the color's alpha value will be set to
-    // the display's transparency (set with setOpacity()), otherwise the background
+    // the display's transparency (set with setBackgroundOpacity()), otherwise the background
     // will be drawn fully opaque
     void drawBackground(QPainter &painter, const QRect &rect, const QColor &color, bool useOpacitySetting);
     // draws the cursor character
@@ -944,7 +945,7 @@ private:
 
     QSize _size;
 
-    qreal _opacity;
+    qreal _backgroundOpacity;
 
     // list of filters currently applied to the display.  used for links and
     // search highlight
diff --git a/src/contents/ui/TerminalPage.qml b/src/contents/ui/TerminalPage.qml
index 502b171..0e3dd2f 100644
--- a/src/contents/ui/TerminalPage.qml
+++ b/src/contents/ui/TerminalPage.qml
@@ -468,7 +468,7 @@ Kirigami.Page {
                         font.pixelSize: TerminalSettings.fontSize
 
                         colorScheme: TerminalSettings.colorScheme
-                        opacity: TerminalSettings.windowOpacity
+                        backgroundOpacity: TerminalSettings.windowOpacity
 
                         Component.onCompleted: {
                             if (!root.initialSessionCreated) {