IJPL-208969 Islands: Fadeout gradient is missing if 'Squeeze tabs' option is on

(cherry picked from commit a000a5a4ae216a56cf0c62f0aa8c56e033776965)

IJ-CR-194805

GitOrigin-RevId: a0c04b12d7e148b35b9538094cb746b0d439aca1

platform/platform-api/src/com/intellij/ui/tabs/impl/IslandsPainterProvider.kt

@@ -3,9 +3,12 @@ package com.intellij.ui.tabs.impl
 
 import com.intellij.openapi.application.ApplicationManager
 import com.intellij.openapi.components.serviceOrNull
+import com.intellij.ui.tabs.JBTabPainter
 import com.intellij.ui.tabs.JBTabsPosition
 import org.jetbrains.annotations.ApiStatus
+import java.awt.Color
 import java.awt.Insets
+import javax.swing.JComponent
 
 @ApiStatus.Experimental
 @ApiStatus.Internal
@@ -19,9 +22,16 @@ open class IslandsPainterProvider {
 
   open fun useMacScrollBar(): Boolean = false
 
-  open fun isTabOccupiesWholeHeight(): Boolean = true
-
   open fun getSingleRowTabInsets(tabsPosition: JBTabsPosition): Insets? = null
 
   open fun isRoundedTabDuringDrag(): Boolean = false
+
+  open fun getEditorTabComposedBgColor(
+    component: JComponent,
+    tabPainter: JBTabPainter,
+    tabColor: Color?,
+    active: Boolean,
+    hovered: Boolean,
+    selected: Boolean,
+  ): Color? = null
 }

platform/platform-api/src/com/intellij/ui/tabs/impl/TabLabel.kt

@@ -22,6 +22,7 @@ import com.intellij.ui.ClientProperty
 import com.intellij.ui.ColorUtil
 import com.intellij.ui.ExperimentalUI.Companion.isNewUI
 import com.intellij.ui.InplaceButton
+import com.intellij.ui.IslandsState
 import com.intellij.ui.LayeredIcon
 import com.intellij.ui.RelativeFont
 import com.intellij.ui.SimpleColoredComponent
@@ -347,8 +348,8 @@ open class TabLabel @Internal constructor(
   protected fun paintFadeout(g: Graphics) {
     val g2d = g.create() as Graphics2D
     try {
-      val isTabOccupiesWholeHeight = IslandsPainterProvider.getInstance()?.isTabOccupiesWholeHeight() != false
-      val tabBg = if (isTabOccupiesWholeHeight) effectiveBackground else tabs.tabPainter.getBackgroundColor()
+      val isIslands = IslandsState.isEnabled()
+      val tabBg = if (isIslands) tabs.tabPainter.getBackgroundColor() else effectiveBackground
       val transparent = ColorUtil.withAlpha(tabBg, 0.0)
       val borderThickness = tabs.borderThickness
       val width = JBUI.scale(MathUtil.clamp(Registry.intValue("ide.editor.tabs.fadeout.width", 10), 1, 200))
@@ -364,8 +365,18 @@ open class TabLabel @Internal constructor(
       val contentRect = labelPlaceholder.bounds
       // Fadeout for right side before pin/close button (needed only in side placements and in squeezing layout)
       if (contentRect.width < labelPlaceholder.preferredSize.width + tabs.tabHGap) {
-        if (isTabOccupiesWholeHeight) { // Can be implemented later for isTabOccupiesWholeHeight
-          val rightRect = Rectangle(contentRect.x + contentRect.width - width, borderThickness, width, rect.height - 2 * borderThickness)
+        val rightRect = Rectangle(contentRect.x + contentRect.width - width, borderThickness, width, rect.height - 2 * borderThickness)
+        if (isIslands) {
+          val composedBg = IslandsPainterProvider.getInstance()?.getEditorTabComposedBgColor(
+            tabs, tabs.tabPainter, info.tabColor, tabs.isActiveTabs(info), isHovered, isSelected)
+          if (composedBg != null) {
+            val labelCoord = SwingUtilities.convertPoint(label, 0, 0, this)
+            rightRect.y = labelCoord.y
+            rightRect.height = label.height
+            paintGradientRect(g2d, rightRect, ColorUtil.withAlpha(composedBg, 0.0), composedBg)
+          }
+        }
+        else {
           paintGradientRect(g2d, rightRect, transparent, tabBg)
         }
       }

platform/platform-impl/src/com/intellij/openapi/application/impl/InternalUICustomization.kt

@@ -94,8 +94,6 @@ open class InternalUICustomization {
 
   open val isMainMenuBottomBorder: Boolean = true
 
-  open val isTabOccupiesWholeHeight: Boolean = true
-
   open val isRoundedTabDuringDrag: Boolean = false
 
   internal open fun configureToolWindowPane(toolWindowPaneParent: JComponent, buttonManager: ToolWindowButtonManager) {}

platform/platform-impl/src/com/intellij/openapi/application/impl/islands/IslandsInternalPainterProvider.kt

@@ -2,10 +2,13 @@
 package com.intellij.openapi.application.impl.islands
 
 import com.intellij.openapi.application.impl.InternalUICustomization
+import com.intellij.ui.tabs.JBTabPainter
 import com.intellij.ui.tabs.JBTabsPosition
 import com.intellij.ui.tabs.impl.IslandsPainterProvider
 import com.intellij.ui.tabs.impl.TabPainterAdapter
+import java.awt.Color
 import java.awt.Insets
+import javax.swing.JComponent
 
 internal class IslandsInternalPainterProvider : IslandsPainterProvider() {
   override fun createCommonTabPainter(): TabPainterAdapter? {
@@ -16,11 +19,6 @@ internal class IslandsInternalPainterProvider : IslandsPainterProvider() {
     return InternalUICustomization.getInstance()?.isMacScrollBar == true
   }
 
-  override fun isTabOccupiesWholeHeight(): Boolean {
-    val customization = InternalUICustomization.getInstance()
-    return customization?.isTabOccupiesWholeHeight ?: super.isTabOccupiesWholeHeight()
-  }
-
   override fun getSingleRowTabInsets(tabsPosition: JBTabsPosition): Insets? {
     val customization = InternalUICustomization.getInstance()
     return if (customization == null) super.getSingleRowTabInsets(tabsPosition) else customization.getSingleRowTabInsets(tabsPosition)
@@ -29,4 +27,15 @@ internal class IslandsInternalPainterProvider : IslandsPainterProvider() {
   override fun isRoundedTabDuringDrag(): Boolean {
     return InternalUICustomization.getInstance()?.isRoundedTabDuringDrag == true
   }
+
+  override fun getEditorTabComposedBgColor(
+    component: JComponent,
+    tabPainter: JBTabPainter,
+    tabColor: Color?,
+    active: Boolean,
+    hovered: Boolean,
+    selected: Boolean,
+  ): Color? {
+    return (tabPainter as? IslandsTabPainter)?.getEditorTabComposedBgColor(component, tabColor, active, hovered, selected)
+  }
 }

platform/platform-impl/src/com/intellij/openapi/application/impl/islands/IslandsTabPainter.kt

@@ -26,6 +26,7 @@ import java.awt.Graphics
 import java.awt.Graphics2D
 import java.awt.Point
 import java.awt.Rectangle
+import javax.swing.JComponent
 import kotlin.math.floor
 
 internal class IslandsTabPainterAdapter(isDefault: Boolean, debugger: Boolean, var isEnabled: Boolean) : TabPainterAdapter {
@@ -191,6 +192,29 @@ internal open class IslandsTabPainter(isDefault: Boolean, isToolWindow: Boolean)
     RectanglePainter2D.DRAW.paint(g, x, y, width, height, arc)
   }
 
+  /**
+   * Calculates the composed background color for editor tabs. The resulting color is not transparent,
+   * see [paintTab] for details.
+   */
+  fun getEditorTabComposedBgColor(
+    component: JComponent,
+    tabColor: Color?,
+    active: Boolean,
+    hovered: Boolean,
+    selected: Boolean,
+  ): Color {
+    var result = if (myFillBackground) getBackgroundColor() else UIUtil.getBgFillColor(component)
+
+    if (tabColor != null) {
+      result = ColorUtil.alphaBlending(ColorUtil.withAlpha(tabColor, 0.9), result)
+    }
+
+    val (fill, _) = getColors(active, hovered, selected)
+    result = ColorUtil.alphaBlending(fill, result)
+
+    return result
+  }
+
   private val hoverBackground = JBColor("EditorTabs.hoverBackground", JBColor(Color(0xE5, 0xEE, 0xFF, 0x80), Color(0x34, 0x3E, 0x51, 0x80)))
 
   private val inactiveBorderColor = JBColor("EditorTabs.inactiveUnderlinedTabBorderColor", JBColor(Color(0x7F, 0x99, 0xC3, 0x80), Color(0x7F, 0x99, 0xC3, 0x80)))

platform/platform-impl/src/com/intellij/openapi/application/impl/islands/IslandsUICustomization.kt

@@ -197,9 +197,6 @@ internal class IslandsUICustomization : InternalUICustomization() {
       return !isManyIslandEnabled
     }
 
-  override val isTabOccupiesWholeHeight: Boolean
-    get() = !isManyIslandEnabled
-
   override val isRoundedTabDuringDrag: Boolean
     get() = isManyIslandEnabled && (WindowRoundedCornersManager.isAvailable() || StartupUiUtil.isWaylandToolkit())