Put the indicator on the screen the session is actually on

The indicator asked QCursor.pos() which screen to appear on, and Wayland tells a client where the pointer is only while it is over one of that client's own windows. The indicator is never under the pointer, so the answer came back stale, or at the origin when the pointer had never been over a window of ours. Measured on Plasma 6: the origin under the Wayland platform, and a point frozen for the whole run through XWayland, which is the platform Dikte actually uses. Every indicator therefore landed in the corner of whichever screen holds 0,0, which on a two monitor desk is the wrong screen most of the time.

KWin knows, and answers for it over D-Bus with activeOutputName, naming outputs the way Qt names screens: by connector, natively and through XWayland alike. That answer now comes before the pointer, and the pointer still decides everywhere else, which is right on X11 and no worse than before on other Wayland desktops. It is the active output and not the pointer's, so on Plasma the two are the same screen only where the active screen is set to follow the mouse, and otherwise it is the focused window that decides, which is where the typing is going anyway. Nothing in the settings window promises the pointer any more.

Deciding the screen once, when the indicator appears, leaves it behind when the work moves to another monitor mid-recording, so overlay_follows_pointer keeps it up to date while it is up. Off by default: a ribbon that changes desks mid-sentence is one more thing moving while you are trying to talk. The compositor is asked four times a second rather than at the ribbon's 33 ms, because a hand moving a mouse across a desk is slower than that, and the call is given a 200 ms timeout so a wedged compositor cannot freeze the indicator with it.

One indicator stacking on another takes that one's screen and never asks for its own. Asked for itself it would answer where the session is now, which is not where the ribbon underneath was put a minute ago, and the pair would end up a monitor apart with the top one raised over nothing. That one is checked every tick, since its answer costs nothing.

dikte/settings_ui.py

@@ -867,7 +867,11 @@ class SettingsWindow(QDialog):
         form = QFormLayout(page)
 
         self.indicator_screen = QComboBox()
-        self.indicator_screen.addItem(t("Follow the mouse pointer"), "")
+        # The active screen rather than the pointer, for the reason in
+        # overlay._compositor_screen: it is what a compositor will answer for,
+        # and on Plasma the two are one screen only where the active screen is
+        # set to follow the mouse.
+        self.indicator_screen.addItem(t("Follow the active screen"), "")
         for screen in QGuiApplication.screens():
             # The native resolution, so that a scaled 4K screen reads
             # 3840 × 2160 and not the 1920 × 1080 Qt sees through the scale.
@@ -881,12 +885,26 @@ class SettingsWindow(QDialog):
             )
         form.addRow(t("Indicator screen"), self.indicator_screen)
 
+        # Only the screen it appeared on is decided when it appears; this is
+        # what makes it keep up with a session that moves to another one
+        # mid-recording. The active screen and not the pointer, because that is
+        # what a compositor will answer for: on Plasma the two are the same
+        # screen only where the active screen is set to follow the mouse, and
+        # otherwise it is the focused window that decides. Nothing to offer
+        # when a screen is named above, since that name is the whole answer.
+        self.follow_pointer = QCheckBox(t("Move it when the active screen changes"))
+        self.indicator_screen.currentIndexChanged.connect(self._sync_follow_pointer)
+        form.addRow("", self.follow_pointer)
+
         self.corner = QComboBox()
         for value in CORNERS:
             self.corner.addItem(t(value), value)
         form.addRow(t("Indicator corner"), self.corner)
         return page
 
+    def _sync_follow_pointer(self):
+        self.follow_pointer.setEnabled(not self.indicator_screen.currentData())
+
     def _api_tab(self):
         page = QWidget()
         outer = QVBoxLayout(page)
@@ -1805,6 +1823,8 @@ class SettingsWindow(QDialog):
         if screen_name and self.indicator_screen.findData(screen_name) < 0:
             self.indicator_screen.addItem(t("{name} (not connected)", name=screen_name), screen_name)
         self._select_data(self.indicator_screen, screen_name)
+        self.follow_pointer.setChecked(conf["overlay_follows_pointer"])
+        self._sync_follow_pointer()
         self._select_data(self.corner, conf["overlay_corner"])
         self.max_seconds.setValue(conf["max_seconds"])
         self.skip_silent.setChecked(conf["skip_silent"])
@@ -1925,6 +1945,9 @@ class SettingsWindow(QDialog):
         conf["paste_shortcut"] = self.paste_shortcut.currentText().strip()
         conf["restore_clipboard"] = self.restore_clipboard.isChecked()
         conf["overlay_screen"] = self.indicator_screen.currentData() or ""
+        # Read even while it is greyed out, so that naming a screen and taking
+        # the name back again does not clear a preference nobody touched.
+        conf["overlay_follows_pointer"] = self.follow_pointer.isChecked()
         conf["overlay_corner"] = self.corner.currentData() or "bottom-left"
         conf["max_seconds"] = self.max_seconds.value()
         conf["skip_silent"] = self.skip_silent.isChecked()