instead of denying Mode changes, just open a new Editor window (resolves #189)

app/src/processing/app/Base.java

@@ -940,9 +940,7 @@ public class Base {
 
 
   /**
-   * The call has already checked to make sure this sketch is not modified,
-   * now change the mode.
-   * @return true if mode is changed.
+   * @return true if mode is changed within this window (false if new window)
    */
   public boolean changeMode(Mode mode) {
     Mode oldMode = activeEditor.getMode();
@@ -950,25 +948,22 @@ public class Base {
       Sketch sketch = activeEditor.getSketch();
       nextMode = mode;
 
-      if (sketch.isUntitled()) {
+      if (sketch.isModified()) {
+        handleNew();  // don't bother with error messages, just switch
+        return false;
+
+      } else if (sketch.isUntitled()) {
         // The current sketch is empty, just close and start fresh.
         // (Otherwise the editor would lose its 'untitled' status.)
         handleClose(activeEditor, true);
         handleNew();
 
       } else {
-        // If the current editor contains file extensions that the new mode can handle, then
-        // write a sketch.properties file with the new mode specified, and reopen.
-        boolean newModeCanHandleCurrentSource = true;
-        for (final SketchCode code : sketch.getCode()) {
-          if (!mode.validExtension(code.getExtension())) {
-            newModeCanHandleCurrentSource = false;
-            break;
-          }
-        }
-        if (!newModeCanHandleCurrentSource) {
-          return false;
-        } else {
+        // If the current sketch contains file extensions that the new mode
+        // can handle, then write a sketch.properties file with the new mode
+        // specified, and reopen. (Really only useful for Java <-> Android)
+        //if (isCompatible(sketch, mode)) {
+        if (mode.canEdit(sketch)) {
           final File props = new File(sketch.getCodeFolder(), "sketch.properties");
           saveModeSettings(props, nextMode);
           handleClose(activeEditor, true);
@@ -980,11 +975,27 @@ public class Base {
             handleOpen(sketch.getMainFilePath());
             return false;
           }
+        } else {
+          handleNew();  // create a new window with the new Mode
+          return false;
         }
       }
     }
+    // Against all (or at least most) odds, we were able to reassign the Mode
+    return true;
+  }
+
+
+  /*
+  private boolean isCompatible(Sketch sketch, Mode mode) {
+    for (final SketchCode code : sketch.getCode()) {
+      if (!mode.validExtension(code.getExtension())) {
+        return false;
+      }
+    }
     return true;
   }
+  */
 
 
   private static class ModeInfo {

app/src/processing/app/Mode.java

@@ -949,6 +949,17 @@ public abstract class Mode {
     return validExtension(f.getName().substring(dot + 1));
   }
 
+
+  public boolean canEdit(Sketch sketch) {
+    for (final SketchCode code : sketch.getCode()) {
+      if (!validExtension(code.getExtension())) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+
   /**
    * Check this extension (no dots, please) against the list of valid
    * extensions.

app/src/processing/app/ui/Editor.java

@@ -529,6 +529,7 @@ public abstract class Editor extends JFrame implements RunnerListener {
     for (final Mode m : base.getModeList()) {
       JRadioButtonMenuItem item = new JRadioButtonMenuItem(m.getTitle());
       item.addActionListener(e -> {
+        /*
         if (!sketch.isModified()) {
           if (!base.changeMode(m)) {
             reselectMode();
@@ -540,6 +541,14 @@ public abstract class Editor extends JFrame implements RunnerListener {
           Messages.showWarning("Save",
                                "Please save the sketch before changing the mode.");
         }
+        */
+        //if (sketch.isModified() || !base.changeMode(m)) {
+        if (!base.changeMode(m)) {
+          // Returns false if unable to change the mode in this window
+          // (which will open a new window with the new Mode), in which case
+          // re-select the menu item b/c Java changes it automatically.
+          reselectMode();
+        }
       });
       modePopup.add(item);
       modeGroup.add(item);

todo.txt

@@ -17,6 +17,10 @@ X set args for JavaFX and OpenGL for the mouse and key events
 X   make sure that everything is set properly, also for keys
 X move ISSUE_TEMPLATE to .github subfolder
 X   https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/manually-creating-a-single-issue-template-for-your-repository
+o ability to switch mode in p5 w/o saving/closing/etc
+X   trying to save the user from themselves here is just messier than needed
+X   opt to open a new editor window rather than weird error messages
+X   https://github.com/processing/processing4/issues/189
 
 readme
 X was fixed in the source for 4.0a5, but may not have been included in the dist
@@ -170,9 +174,6 @@ _   better for git, etc
 _   single file thing is long gone
 _   introduce the idea of 'scraps' (ala gist) that are just single page blobs
 _ launch/psk files/import from web editor (more details below)
-_ ability to switch mode in p5 w/o saving/closing/etc
-_   trying to save the user from themselves here is just messier than needed
-_   https://github.com/processing/processing4/issues/189
 _ cleaning up the temp file handling
 _   'show sketch folder' weird when in temp folder
 _     ask to save first (sketch has not been saved yet)