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

atom/browser/native_window_mac.mm

@@ -22,6 +22,7 @@
 #include "atom/common/options_switches.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
+#include "base/numerics/ranges.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/remote_cocoa/app_shim/bridged_native_widget_impl.h"
 #include "content/public/browser/browser_accessibility_state.h"
@@ -1047,7 +1048,8 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 void NativeWindowMac::SetOpacity(const double opacity) {
-  [window_ setAlphaValue:opacity];
+  const double boundedOpacity = base::ClampToRange(opacity, 0.0, 1.0);
+  [window_ setAlphaValue:boundedOpacity];
 }
 
 double NativeWindowMac::GetOpacity() {

atom/browser/native_window_views.cc

@@ -25,6 +25,7 @@
 #include "atom/common/draggable_region.h"
 #include "atom/common/native_mate_converters/image_converter.h"
 #include "atom/common/options_switches.h"
+#include "base/numerics/ranges.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/browser_thread.h"
 #include "native_mate/dictionary.h"
@@ -866,16 +867,19 @@ bool NativeWindowViews::HasShadow() {
 
 void NativeWindowViews::SetOpacity(const double opacity) {
 #if defined(OS_WIN)
+  const double boundedOpacity = base::ClampToRange(opacity, 0.0, 1.0);
   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_ = 1.0;  // setOpacity unsupported on Linux
 #endif
-  opacity_ = opacity;
 }
 
 double NativeWindowViews::GetOpacity() {

spec/api-browser-window-spec.js

@@ -1214,24 +1214,48 @@ describe('BrowserWindow module', () => {
   })
 
   describe('BrowserWindow.setOpacity(opacity)', () => {
-    it('make window with initial opacity', () => {
-      w.destroy()
-      w = new BrowserWindow({
-        show: false,
-        width: 400,
-        height: 400,
-        opacity: 0.5
+    describe('Windows and Mac', function () {
+      if (process.platform === 'linux') {
+        this.skip()
+      }
+
+      it('make window with initial opacity', () => {
+        const w = new BrowserWindow({ show: false, opacity: 0.5 })
+        expect(w.getOpacity()).to.equal(0.5)
+      })
+
+      it('allows setting the opacity', () => {
+        const w = new BrowserWindow({ show: false })
+        expect(() => {
+          w.setOpacity(0.0)
+          expect(w.getOpacity()).to.equal(0.0)
+          w.setOpacity(0.5)
+          expect(w.getOpacity()).to.equal(0.5)
+          w.setOpacity(1.0)
+          expect(w.getOpacity()).to.equal(1.0)
+        }).to.not.throw()
+      })
+
+      it('clamps opacity to [0.0...1.0]', () => {
+        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)
       })
-      assert.strictEqual(w.getOpacity(), 0.5)
     })
-    it('allows setting the opacity', () => {
-      assert.doesNotThrow(() => {
-        w.setOpacity(0.0)
-        assert.strictEqual(w.getOpacity(), 0.0)
+
+    describe('Linux', function () {
+      if (process.platform !== 'linux') {
+        this.skip()
+      }
+
+      it('sets 1 regardless of parameter', () => {
+        const w = new BrowserWindow({ show: false })
+        w.setOpacity(0)
+        expect(w.getOpacity()).to.equal(1.0)
         w.setOpacity(0.5)
-        assert.strictEqual(w.getOpacity(), 0.5)
-        w.setOpacity(1.0)
-        assert.strictEqual(w.getOpacity(), 1.0)
+        expect(w.getOpacity()).to.equal(1.0)
       })
     })
   })