V3 alpha - calling window id and name (wailsapp#3888)

* Add the calling window name and ID to the context if available. Update the documentation.

* Update changelog.md

mkdocs-website/docs/en/changelog.md

@@ -27,6 +27,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - New `InitialPosition` option to specify if the window should be centered or positioned at the given X/Y location by [leaanthony](https://github.com/leaanthony) in [#3885](https://github.com/wailsapp/wails/pull/3885)
 - Add `Path` & `Paths` methods to `application` package by [ansxuman](https://github.com/ansxuman) and [leaanthony](https://github.com/leaanthony) in [#3823](https://github.com/wailsapp/wails/pull/3823)
 - Added `GeneralAutofillEnabled` and `PasswordAutosaveEnabled` Windows options by [leaanthony](https://github.com/leaanthony) in [#3766](https://github.com/wailsapp/wails/pull/3766)
+- Added the ability to retrieve the window calling a service method by [leaanthony](https://github.com/leaanthony)
+  in [#3888](https://github.com/wailsapp/wails/pull/3888)
 
 ### Changed
 - Asset embed to include `all:frontend/dist` to support frameworks that generate subfolders by @atterpac in [#3887](https://github.com/wailsapp/wails/pull/3887)

mkdocs-website/docs/en/learn/bindings.md

@@ -329,3 +329,50 @@ export class Person {
 ```
 
 Using TypeScript bindings provides type safety and improved IDE support when working with the generated code in your frontend.
+
+### Using `context.Context`
+
+When defining service methods in Go, you can include `context.Context` as the first parameter. The runtime will automatically provide a context when the method is called from the frontend.
+
+The context provides several powerful features:
+
+1. **Cancellation Support**: Long-running operations can be cancelled from the frontend, which will raise an error through the Promise chain.
+
+2. **Window Information**: You can determine which window made the call using these context keys:
+   - `application.WindowNameKey` - Returns the name of the calling window
+   - `application.WindowIDKey` - Returns the ID of the calling window
+
+Here are some examples:
+
+```go
+// Basic context usage with cancellation
+func (s *MyService) LongRunningTask(ctx context.Context, input string) (string, error) {
+    select {
+	// Check if the context has been cancelled from the frontend
+    case <-ctx.Done():
+        return "", ctx.Err()
+    default:
+        // Process task
+        return "completed", nil
+    }
+}
+
+// Getting caller window information
+func (s *MyService) WindowAwareMethod(ctx context.Context) (string, error) {
+    windowName := ctx.Value(application.WindowNameKey).(string)
+    windowID := ctx.Value(application.WindowIDKey).(string)
+    return fmt.Sprintf("Called from window: %s (ID: %s)", windowName, windowID), nil
+}
+```
+
+From the frontend, these methods can be called normally. If you need to cancel a long-running operation, the Promise will be rejected with the cancellation error:
+
+```javascript
+// Call the method
+const promise = MyService.LongRunningTask("input");
+
+// Cancel it later if needed
+// This will cause the context to be cancelled in the Go method
+promise.cancel();
+```
+

v3/pkg/application/messageprocessor_call.go

@@ -7,8 +7,12 @@ import (
 	"net/http"
 )
 
+type contextKey string
+
 const (
-	CallBinding = 0
+	CallBinding              = 0
+	WindowNameKey contextKey = "WindowName"
+	WindowIDKey   contextKey = "WindowID"
 )
 
 func (m *MessageProcessor) callErrorCallback(window Window, message string, callID *string, err error) {
@@ -95,6 +99,12 @@ func (m *MessageProcessor) processCallMethod(method int, rw http.ResponseWriter,
 			return
 		}
 
+		// Set the context values for the window
+		if window != nil {
+			ctx = context.WithValue(ctx, WindowNameKey, window.Name())
+			ctx = context.WithValue(ctx, WindowIDKey, window.ID())
+		}
+
 		go func() {
 			defer func() {
 				cancel()
@@ -123,7 +133,11 @@ func (m *MessageProcessor) processCallMethod(method int, rw http.ResponseWriter,
 			var jsonArgs struct {
 				Args json.RawMessage `json:"args"`
 			}
-			params.ToStruct(&jsonArgs)
+			err = params.ToStruct(&jsonArgs)
+			if err != nil {
+				m.callErrorCallback(window, "Error parsing arguments: %s", callID, err)
+				return
+			}
 			m.Info("Call Binding:", "method", boundMethod, "args", string(jsonArgs.Args), "result", result)
 		}()
 		m.ok(rw)