fix: normalize behavior of win.setOpacity() for invalid number values across operating systems

docs/api/browser-window.md

@@ -1455,11 +1455,13 @@ On Windows and Linux always returns
 
 * `opacity` Number - between 0.0 (fully transparent) and 1.0 (fully opaque)
 
-Sets the opacity of the window. On Linux does nothing.
+Sets the opacity of the window. On Linux, does nothing. Out of bound number
+values are clamped to the [0, 1] range.
 
 #### `win.getOpacity()` _Windows_ _macOS_
 
-Returns `Number` - between 0.0 (fully transparent) and 1.0 (fully opaque)
+Returns `Number` - between 0.0 (fully transparent) and 1.0 (fully opaque). On
+Linux, always returns 1.
 
 #### `win.setShape(rects)` _Windows_ _Linux_ _Experimental_
 

shell/browser/native_window_mac.mm

@@ -1032,7 +1032,14 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 void NativeWindowMac::SetOpacity(const double opacity) {
-  [window_ setAlphaValue:opacity];
+  double boundedOpacity = opacity;
+  if (opacity < 0) {
+    boundedOpacity = 0;
+  } else if (opacity > 1) {
+    boundedOpacity = 1;
+  }
+
+  [window_ setAlphaValue:boundedOpacity];
 }
 
 double NativeWindowMac::GetOpacity() {

shell/browser/native_window_views.cc

@@ -880,16 +880,25 @@ bool NativeWindowViews::HasShadow() {
 
 void NativeWindowViews::SetOpacity(const double opacity) {
 #if defined(OS_WIN)
+  double boundedOpacity = opacity;
+  if (opacity > 1) {
+    boundedOpacity = 1;
+  } else if (opacity < 0) {
+    boundedOpacity = 0;
+  }
+
   HWND hwnd = GetAcceleratedWidget();
   if (!layered_) {
     LONG ex_style = ::GetWindowLong(hwnd, GWL_EXSTYLE);
     ex_style |= WS_EX_LAYERED;
     ::SetWindowLong(hwnd, GWL_EXSTYLE, ex_style);
     layered_ = true;
   }
-  ::SetLayeredWindowAttributes(hwnd, 0, opacity * 255, LWA_ALPHA);
+  ::SetLayeredWindowAttributes(hwnd, 0, boundedOpacity * 255, LWA_ALPHA);
+  opacity_ = boundedOpacity;
+#else
+  opacity_ = 1;  // setOpacity unsupported on Linux
 #endif
-  opacity_ = opacity;
 }
 
 double NativeWindowViews::GetOpacity() {

spec-main/api-browser-window-spec.ts

@@ -7,13 +7,11 @@ import * as qs from 'querystring'
 import * as http from 'http'
 import { AddressInfo } from 'net'
 import { app, BrowserWindow, BrowserView, ipcMain, OnBeforeSendHeadersListenerDetails, protocol, screen, webContents, session, WebContents } from 'electron'
-import { emittedOnce } from './events-helpers';
-import { closeWindow } from './window-helpers';
+import { emittedOnce } from './events-helpers'
+import { ifit, ifdescribe } from './spec-helpers'
+import { closeWindow } from './window-helpers'
 const { expect } = chai
 
-const ifit = (condition: boolean) => (condition ? it : it.skip)
-const ifdescribe = (condition: boolean) => (condition ? describe : describe.skip)
-
 chai.use(chaiAsPromised)
 
 const fixtures = path.resolve(__dirname, '..', 'spec', 'fixtures')
@@ -1240,7 +1238,8 @@ describe('BrowserWindow module', () => {
     })
   })
 
-  describe('BrowserWindow.setOpacity(opacity)', () => {
+
+  ifdescribe(process.platform !== 'linux')('BrowserWindow.setOpacity(opacity)', () => {
     afterEach(closeAllWindows)
     it('make window with initial opacity', () => {
       const w = new BrowserWindow({ show: false, opacity: 0.5 })
@@ -1257,6 +1256,14 @@ describe('BrowserWindow module', () => {
         expect(w.getOpacity()).to.equal(1.0)
       }).to.not.throw()
     })
+
+    it('does not change opacity if given number out of bounds', () => {
+      const w = new BrowserWindow({ show: false, opacity: 0.5 })
+      w.setOpacity(100)
+      expect(w.getOpacity()).to.equal(1.0)
+      w.setOpacity(-100)
+      expect(w.getOpacity()).to.equal(0.0)
+    })
   })
 
   describe('BrowserWindow.setShape(rects)', () => {