Rename ITheme.selection to selectionBackground

This makes it consistent with selectionForeground and other theme keys and
as a result will make the API easier to work with, especially when inactive
selection is done (#3803)

addons/xterm-addon-canvas/src/SelectionRenderLayer.ts

@@ -85,7 +85,7 @@ export class SelectionRenderLayer extends BaseRenderLayer {
       return;
     }
 
-    this._ctx.fillStyle = this._colors.selectionTransparent.css;
+    this._ctx.fillStyle = this._colors.selectionBackgroundTransparent.css;
 
     if (columnSelectMode) {
       const startCol = start[0];

addons/xterm-addon-canvas/src/atlas/CharAtlasUtils.ts

@@ -15,7 +15,7 @@ export function generateConfig(scaledCharWidth: number, scaledCharHeight: number
     background: colors.background,
     cursor: undefined,
     cursorAccent: undefined,
-    selection: undefined,
+    selectionBackground: undefined,
     ansi: colors.ansi.slice()
   };
   return {

addons/xterm-addon-webgl/src/WebglRenderer.ts

@@ -405,7 +405,7 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
     // Apply the selection color if needed
     if (this._isCellSelected(x, y)) {
-      bgOverride = this._colors.selectionOpaque.rgba >> 8 & 0xFFFFFF;
+      bgOverride = this._colors.selectionBackgroundOpaque.rgba >> 8 & 0xFFFFFF;
       if (this._colors.selectionForeground) {
         fgOverride = this._colors.selectionForeground.rgba >> 8 & 0xFFFFFF;
       }

addons/xterm-addon-webgl/src/atlas/CharAtlasUtils.ts

@@ -21,8 +21,8 @@ export function generateConfig(scaledCellWidth: number, scaledCellHeight: number
     background: colors.background,
     cursor: NULL_COLOR,
     cursorAccent: NULL_COLOR,
-    selectionTransparent: NULL_COLOR,
-    selectionOpaque: NULL_COLOR,
+    selectionBackgroundTransparent: NULL_COLOR,
+    selectionBackgroundOpaque: NULL_COLOR,
     selectionForeground: NULL_COLOR,
     // For the static char atlas, we only use the first 16 colors, but we need all 256 for the
     // dynamic character atlas.

addons/xterm-addon-webgl/test/WebglRenderer.api.ts

@@ -843,7 +843,7 @@ describe('WebGL Renderer Integration Tests', async () => {
       const theme: ITheme = {
         foreground: '#FF0000',
         background: '#00FF00',
-        selection: '#0000FF'
+        selectionBackground: '#0000FF'
       };
       await page.evaluate(`window.term.options.theme = ${JSON.stringify(theme)};`);
       await writeSync(page, ` █\\x1b[7m█\\x1b[0m`);