Merge pull request #1217 from liangforstudy/fix-movable-dialogs

dialogs: drag them by the title bar (open centred, no longer anchored)

crates/ui-egui/src/lib.rs

@@ -1909,7 +1909,8 @@ impl FilmcraftApp {
             .id(egui::Id::new("FilmCraft hit an error"))
             .collapsible(false)
             .resizable(false)
-            .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+            .pivot(egui::Align2::CENTER_CENTER)
+            .default_pos(crate::widgets::dialog_center(ctx))
             .show(ctx, |ui| {
                 ui.set_max_width(460.0);
                 ui.label(tl!("Something went wrong while drawing the window. Your project is still open; save it to be safe."));

crates/ui-egui/src/panels/clip_dialogs.rs

@@ -30,7 +30,8 @@
 //! - Quit (asked when the window is closed with unsaved changes, see [`intercept_quit`])
 //!   `quit.save`, `quit.dontSave`, `quit.cancel`.
 
-use egui::{Align2, RichText};
+use crate::widgets::CenteredDialog as _;
+use egui::RichText;
 use filmcraft_project::{AudioChannelMap, AudioChannels, ItemKind, TrackKind};
 use serde_json::{Value, json};
 
@@ -311,7 +312,7 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
     let can_save = app.session.path.is_some() || app.hooks.pick_save.is_some();
     // the title is translated; the window keeps one id whatever the interface language
     let id = egui::Id::new(("clip-dialog", pre));
-    egui::Window::new(title).id(id).collapsible(false).resizable(false).default_width(360.0).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(ctx, |ui| {
+    egui::Window::new(title).id(id).collapsible(false).resizable(false).default_width(360.0).centered(ctx).show(ctx, |ui| {
         let p = &mut d.params;
         match d.command.as_str() {
             "edit.pasteAttributes" | "edit.removeAttributes" => {

crates/ui-egui/src/panels/dialogs.rs

@@ -37,7 +37,8 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
                 .open(&mut open)
                 .collapsible(false)
                 .resizable(false)
-                .anchor(egui::Align2::CENTER_CENTER, egui::vec2(0.0, 0.0))
+                .pivot(egui::Align2::CENTER_CENTER)
+                .default_pos(crate::widgets::dialog_center(ctx))
                 .show(ctx, |ui| about(app, ui));
             if crate::widgets::escape_closes(ctx) {
                 open = false;
@@ -112,7 +113,8 @@ fn audio_gain(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .id(egui::Id::new("Audio Gain"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.add_space(6.0);
             egui::Grid::new("audio-gain").num_columns(2).spacing([12.0, 10.0]).show(ui, |ui| {
@@ -200,7 +202,8 @@ fn add_tracks(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .collapsible(false)
         .resizable(false)
         .default_width(320.0)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             // everything spans the width the window has: no empty band beside the fields
             ui.set_width(ui.available_width());
@@ -329,7 +332,8 @@ fn delete_tracks(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .id(egui::Id::new("Delete Tracks"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.set_min_width(300.0);
             for (kind, title, delete, on, target, list) in [

crates/ui-egui/src/panels/graphics.rs

@@ -21,6 +21,7 @@
 //! `program.layer.<clip>.<layer>.corner.<n>`,
 //! `program.textEdit`, `graphics.*` in the panels.
 
+use crate::widgets::CenteredDialog as _;
 use egui::{Align2, Color32, Pos2, Rect, Sense, Stroke, StrokeKind, pos2, vec2};
 use filmcraft_geom::{Affine, Vec2};
 use filmcraft_project::graphic::{self, LayerContent, LayerSpec, eval_layer, layer_display_name, layer_indices};
@@ -1823,7 +1824,7 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
     let mut ok = false;
     let name = |paragraph: bool| if paragraph { tl!("Paragraph Text") } else { tl!("Point Text") };
     let id = egui::Id::new("gfx-text-properties");
-    egui::Window::new(tl!("Text Properties")).id(id).collapsible(false).resizable(false).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(ctx, |ui| {
+    egui::Window::new(tl!("Text Properties")).id(id).collapsible(false).resizable(false).centered(ctx).show(ctx, |ui| {
         ui.label(tl!("Text Layer Type"));
         let r = egui::ComboBox::from_id_salt("gfx-text-type").selected_text(name(d.paragraph)).width(190.0).show_ui(ui, |ui| {
             for paragraph in [false, true] {

crates/ui-egui/src/panels/graphics_templates.rs

@@ -17,6 +17,7 @@
 //! dialogs: `exportTemplate.name|category|control.<n>|ok|cancel`, `replaceFonts.from|to|ok|cancel`.
 //! The UI state (`UiState::gfx_templates`) is serde, so agents can read and set it.
 
+use crate::widgets::CenteredDialog as _;
 use std::sync::Arc;
 
 use egui::{Align2, Color32, Rect, Sense, Stroke, StrokeKind, pos2, vec2};
@@ -650,7 +651,7 @@ fn export_dialog(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .collapsible(false)
         .resizable(false)
         .default_width(420.0)
-        .anchor(Align2::CENTER_CENTER, [0.0, 0.0])
+        .centered(ctx)
         .show(ctx, |ui| {
             egui::Grid::new("gfx-export-grid").num_columns(2).show(ui, |ui| {
                 ui.label(tl!("Name:"));
@@ -729,7 +730,7 @@ fn replace_dialog(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .collapsible(false)
         .resizable(false)
         .default_width(440.0)
-        .anchor(Align2::CENTER_CENTER, [0.0, 0.0])
+        .centered(ctx)
         .show(ctx, |ui| {
             ui.label(tl!("Fonts used in the project:"));
             egui::Grid::new("gfx-fonts-used").striped(true).num_columns(3).show(ui, |ui| {

crates/ui-egui/src/panels/interchange_export.rs

@@ -7,6 +7,7 @@
 //! `<p>.audioFormat.<wav|aiff|mxf>` (mxf: AAF only), `<p>.sampleRate.<rate>`, `<p>.bitDepth.<16|24>`, `<p>.trimAudio`,
 //! `<p>.handles` (frames), `<p>.renderAudioEffects`, `<p>.title` (OMF), `<p>.ok`, `<p>.cancel`.
 
+use crate::widgets::CenteredDialog as _;
 use serde_json::{Value, json};
 
 use crate::FilmcraftApp;
@@ -70,7 +71,7 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
     let mut elems: Vec<(String, egui::Rect, String)> = Vec::new();
     let title = if d.omf { "OMF Export Settings" } else { "AAF Export Settings" };
     let shown = if d.omf { tl!("OMF Export Settings") } else { tl!("AAF Export Settings") };
-    egui::Window::new(shown).id(egui::Id::new(title)).collapsible(false).resizable(false).anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0]).show(ctx, |ui| {
+    egui::Window::new(shown).id(egui::Id::new(title)).collapsible(false).resizable(false).centered(ctx).show(ctx, |ui| {
         ui.set_min_width(380.0);
         egui::Grid::new("interchange-export-grid").num_columns(2).spacing([12.0, 8.0]).show(ui, |ui| {
             if d.omf {

crates/ui-egui/src/panels/media_browser.rs

@@ -806,7 +806,8 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .id(egui::Id::new("mb-edit-columns"))
         .collapsible(false)
         .resizable(false)
-        .anchor(Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             let mut mv: Option<(usize, isize)> = None;
             for c in mb::ALL_COLUMNS {

crates/ui-egui/src/panels/media_dialogs.rs

@@ -166,7 +166,8 @@ fn link_media(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .resizable(false)
         .default_width(width)
         .max_width(width)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             egui::ScrollArea::vertical().id_salt("link-media-body-scroll").max_height((ctx.content_rect().height() - 140.0).max(1.0)).show(ui, |ui| {
                 ui.label(tlf!("{n} clip(s) can't find their media. Locate them, search a folder, or leave them offline.", n = rows.len()));
@@ -373,7 +374,8 @@ fn make_offline(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .id(egui::Id::new("Make Offline"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.label(tlf!("Make {n} selected clip(s) offline. Their clips show the offline slate until you link them again.", n));
             let r = ui.radio(!delete, tl!("Media files remain on disk"));
@@ -417,7 +419,8 @@ fn create_proxies(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .id(egui::Id::new("Create Proxies"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.label(tlf!("{n} clip(s) selected.", n = d.items.len()));
             ui.add_space(4.0);
@@ -496,7 +499,8 @@ fn project_manager(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .id(egui::Id::new("Project Manager"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.label(RichText::new(tl!("Sequences")).strong());
             for (id, name) in &seqs {

crates/ui-egui/src/panels/menu_dialogs.rs

@@ -16,6 +16,7 @@
 //! `find.row.<n>.column|operator|text`; Project Settings tabs `projectSettings.tab.<general|scratchDisks|ingest>`,
 //! scratch rows `projectSettings.scratch.<key>` / `.browse` / `.same`.
 
+use crate::widgets::CenteredDialog as _;
 use egui::{Align2, RichText};
 use filmcraft_project::{FindOp, find::COLUMNS};
 use serde::{Deserialize, Serialize};
@@ -463,7 +464,7 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
     let info_only = matches!(d.command.as_str(), "file.mediaProperties" | "clip.sourceSettings" | "help.systemCompatibilityReport");
     // the title is translated; the window keeps one id whatever the interface language
     let id = egui::Id::new(("menu-dialog", pre));
-    egui::Window::new(title).id(id).collapsible(false).resizable(false).default_width(420.0).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(ctx, |ui| {
+    egui::Window::new(title).id(id).collapsible(false).resizable(false).default_width(420.0).centered(ctx).show(ctx, |ui| {
         let p = &mut d.params;
         match d.command.as_str() {
             "edit.find" => {

crates/ui-egui/src/panels/monitor_view.rs

@@ -803,9 +803,13 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
         GuideDialog::SaveTemplate { .. } => ("Save Guides as Template", tl!("Save Guides as Template")),
         GuideDialog::Manage { .. } => ("Manage Guides", tl!("Manage Guides")),
     };
-    egui::Window::new(shown).id(egui::Id::new(title)).collapsible(false).resizable(false).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(
-        ctx,
-        |ui| match &mut d {
+    egui::Window::new(shown)
+        .id(egui::Id::new(title))
+        .collapsible(false)
+        .resizable(false)
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
+        .show(ctx, |ui| match &mut d {
             GuideDialog::Add { vertical, position, source } => {
                 let m = if *source { "source" } else { "program" };
                 ui.horizontal(|ui| {
@@ -893,8 +897,7 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
                     close |= r.clicked();
                 });
             }
-        },
-    );
+        });
     for (id, r, l) in elems {
         app.auto.add(&id, r, &l);
     }

crates/ui-egui/src/panels/multicam.rs

@@ -108,7 +108,8 @@ pub fn show_dialog(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .collapsible(false)
         .resizable(false)
         .default_width(440.0)
-        .anchor(Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             if pre != "sync" {
                 ui.horizontal(|ui| {
@@ -456,7 +457,8 @@ pub fn show_edit_cameras(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .collapsible(false)
         .resizable(false)
         .default_width(420.0)
-        .anchor(Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.label(RichText::new(tl!("Cameras shown in the Multi-Camera view (uncheck to hide).")).weak().small());
             egui::ScrollArea::vertical().max_height(420.0).show(ui, |ui| {

crates/ui-egui/src/panels/project_dialogs.rs

@@ -3,7 +3,7 @@
 //! and Save Arrangement…. Drafts live in `UiState::project_panel.dialog` (serde, so agents fill
 //! them with `ui.set`); OK runs one engine command.
 
-use egui::Align2;
+use crate::widgets::CenteredDialog as _;
 use serde_json::{Value, json};
 
 use crate::FilmcraftApp;
@@ -25,7 +25,7 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
         ProjectDialog::FreeformOptions { .. } => tl!("Freeform View Options"),
         ProjectDialog::SaveArrangement { .. } => tl!("Save Arrangement"),
     };
-    let mut win = egui::Window::new(title).id(egui::Id::new("project-dialog")).collapsible(false).resizable(false).anchor(Align2::CENTER_CENTER, [0.0, 0.0]);
+    let mut win = egui::Window::new(title).id(egui::Id::new("project-dialog")).collapsible(false).resizable(false).centered(ctx);
     // a fixed size keeps the two-list dialog from shifting while its lists settle
     if matches!(d, ProjectDialog::MetadataDisplay { .. }) {
         win = win.fixed_size(egui::vec2(480.0, 470.0));

crates/ui-egui/src/panels/remix.rs

@@ -52,7 +52,8 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
         .id(egui::Id::new("Remix Properties"))
         .collapsible(false)
         .resizable(false)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.set_min_width(320.0);
             egui::Grid::new("remix-props").num_columns(2).spacing([12.0, 10.0]).show(ui, |ui| {

crates/ui-egui/src/panels/sequence_settings.rs

@@ -491,7 +491,8 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .collapsible(false)
         .resizable(false)
         .default_width(620.0)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.set_width(620.0);
             ui.horizontal(|ui| {

crates/ui-egui/src/panels/shortcuts_dialog.rs

@@ -156,7 +156,8 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .collapsible(false)
         .resizable(false)
         .fixed_size(size)
-        .anchor(Align2::CENTER_CENTER, vec2(0.0, 0.0))
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .frame(egui::Frame::window(&ctx.global_style()).fill(t.panel_bg).inner_margin(14.0))
         .show(ctx, |ui| {
             ui.set_width(size.x);

crates/ui-egui/src/panels/transition_controls.rs

@@ -507,7 +507,8 @@ pub fn duration_dialog(app: &mut FilmcraftApp, ctx: &egui::Context) -> bool {
         .collapsible(false)
         .resizable(false)
         .default_width(260.0)
-        .anchor(egui::Align2::CENTER_CENTER, [0.0, 0.0])
+        .pivot(egui::Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
         .show(ctx, |ui| {
             ui.horizontal(|ui| {
                 ui.label(tl!("Duration:"));

crates/ui-egui/src/panels/voiceover.rs

@@ -11,6 +11,7 @@
 //! `voiceover.ok`, `voiceover.cancel`; the countdown overlay is `voiceover.countdown.overlay`.
 //! UI commands: `voiceover.recordToggle {track?}` and `voiceover.settingsDialog`.
 
+use crate::widgets::CenteredDialog as _;
 use egui::{Align2, Color32, Rect, RichText, Sense, Stroke, pos2, vec2};
 use filmcraft_engine::voiceover::VoiceOverPrefs;
 use filmcraft_project::TrackId;
@@ -239,7 +240,7 @@ fn settings_dialog(app: &mut FilmcraftApp, ctx: &egui::Context) {
     let accent = app.tokens.accent;
     // the title is translated; the window keeps one id whatever the interface language
     let id = egui::Id::new("voiceover-settings");
-    egui::Window::new(tl!("Voice-Over Record Settings")).id(id).collapsible(false).resizable(false).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(ctx, |ui| {
+    egui::Window::new(tl!("Voice-Over Record Settings")).id(id).collapsible(false).resizable(false).centered(ctx).show(ctx, |ui| {
         egui::Grid::new("voiceover-grid").num_columns(2).spacing([12.0, 8.0]).show(ui, |ui| {
             ui.label(tl!("Name:"));
             let r = ui.add(egui::TextEdit::singleline(&mut d.prefs.name).desired_width(220.0));

crates/ui-egui/src/panels/workspaces.rs

@@ -180,9 +180,13 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
         WorkspaceDialog::SaveAs { .. } => ("New Workspace", tl!("New Workspace")),
         WorkspaceDialog::Edit { .. } => ("Edit Workspaces", tl!("Edit Workspaces")),
     };
-    egui::Window::new(shown).id(egui::Id::new(title)).collapsible(false).resizable(false).anchor(Align2::CENTER_CENTER, [0.0, 0.0]).show(
-        ctx,
-        |ui| match &mut d {
+    egui::Window::new(shown)
+        .id(egui::Id::new(title))
+        .collapsible(false)
+        .resizable(false)
+        .pivot(Align2::CENTER_CENTER)
+        .default_pos(crate::widgets::dialog_center(ctx))
+        .show(ctx, |ui| match &mut d {
             WorkspaceDialog::SaveAs { name } => {
                 ui.horizontal(|ui| {
                     ui.label(tl!("Name:"));
@@ -245,8 +249,7 @@ pub fn dialogs(app: &mut FilmcraftApp, ctx: &egui::Context) {
                     close |= r.clicked();
                 });
             }
-        },
-    );
+        });
     for (id, r, l) in elems {
         app.auto.add(&id, r, &l);
     }

crates/ui-egui/src/widgets.rs

@@ -294,6 +294,24 @@ pub fn dropdown_text(ui: &mut Ui, rect: Rect, text: &str, t: &Tokens, id: egui::
     resp
 }
 
+/// Where dialogs open: the centre of the app window. Dialogs use it as `default_pos` with a
+/// centre pivot instead of `Window::anchor`, which would pin them: egui makes anchored windows
+/// immovable, so they could not be dragged by the title bar.
+pub fn dialog_center(ctx: &egui::Context) -> egui::Pos2 {
+    ctx.content_rect().center()
+}
+
+/// `.pivot(CENTER_CENTER).default_pos(dialog_center(ctx))` in one call, for short window chains.
+pub trait CenteredDialog {
+    fn centered(self, ctx: &egui::Context) -> Self;
+}
+
+impl CenteredDialog for egui::Window<'_> {
+    fn centered(self, ctx: &egui::Context) -> Self {
+        self.pivot(Align2::CENTER_CENTER).default_pos(dialog_center(ctx))
+    }
+}
+
 /// Level meter bar (dBFS), vertical.
 pub fn meter_bar(painter: &egui::Painter, rect: Rect, db: f32, peak_db: f32, t: &Tokens) {
     // Premiere: green gradient (#579f51 → #70dc5d), yellow above −12 dB, red above −3 dB.
@@ -368,4 +386,36 @@ mod tests {
         let range = st.cursor.char_range().map(|c| c.sorted_cursors());
         assert_eq!(range, Some([egui::text::CCursor::new(0), egui::text::CCursor::new(5)]));
     }
+
+    /// Dialogs open centred and can be dragged by their title bar (anchored ones could not).
+    #[test]
+    fn dialogs_open_centered_and_drag() {
+        let ctx = egui::Context::default();
+        let screen = egui::Rect::from_min_size(egui::Pos2::ZERO, egui::vec2(1200.0, 800.0));
+        let frame = |events: Vec<egui::Event>| {
+            let input = egui::RawInput { screen_rect: Some(screen), events, ..Default::default() };
+            let mut rect = egui::Rect::NOTHING;
+            let mut out = ctx.run_ui(input, |ui| {
+                let ctx = ui.ctx().clone();
+                let win = egui::Window::new("Dialog").collapsible(false).resizable(false);
+                if let Some(r) = win.pivot(egui::Align2::CENTER_CENTER).default_pos(super::dialog_center(&ctx)).show(&ctx, |ui| ui.label("body")) {
+                    rect = r.response.rect;
+                }
+            });
+            out.textures_delta.clear();
+            rect
+        };
+        frame(Vec::new());
+        let start = frame(Vec::new());
+        assert!((start.center() - screen.center()).length() < 1.0, "opens centred: {start:?}");
+        let grab = egui::pos2(start.center().x, start.min.y + 8.0);
+        let to = grab + egui::vec2(-200.0, -150.0);
+        let press = |p, pressed| egui::Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() };
+        frame(vec![egui::Event::PointerMoved(grab), press(grab, true)]);
+        frame(vec![egui::Event::PointerMoved(grab + egui::vec2(-100.0, -75.0))]);
+        frame(vec![egui::Event::PointerMoved(to)]);
+        frame(vec![press(to, false)]);
+        let end = frame(Vec::new());
+        assert!((end.center() - (start.center() + egui::vec2(-200.0, -150.0))).length() < 2.0, "moved with the drag: {start:?} -> {end:?}");
+    }
 }