Add auto focus timeline and bezier scale on animation editor

Add a button at the bottom of the animation editor that change the zoom based on the animation length and the bezier scale based on the values and handles of the displayed tracks. The icon and the tooltip of the button change depending if the bezier editor is displayed or not.

Some refactor was made in animation_track_editor.cpp to remove code duplication with the visibility check of the tracks.

This should help with the issue #85826

editor/animation_track_editor.cpp

@@ -1305,7 +1305,11 @@ void AnimationTimelineEdit::_zoom_changed(double) {
 }
 
 float AnimationTimelineEdit::get_zoom_scale() const {
-	float zv = zoom->get_max() - zoom->get_value();
+	return _get_zoom_scale(zoom->get_value());
+}
+
+float AnimationTimelineEdit::_get_zoom_scale(double p_zoom_value) const {
+	float zv = zoom->get_max() - p_zoom_value;
 	if (zv < 1) {
 		zv = 1.0 - zv;
 		return Math::pow(1.0f + zv, 8.0f) * 100;
@@ -1633,6 +1637,68 @@ void AnimationTimelineEdit::set_zoom(Range *p_zoom) {
 	zoom->connect("value_changed", callable_mp(this, &AnimationTimelineEdit::_zoom_changed));
 }
 
+void AnimationTimelineEdit::auto_fit() {
+	if (!animation.is_valid()) {
+		return;
+	}
+
+	float anim_end = animation->get_length();
+	float anim_start = 0;
+
+	// Search for keyframe outside animation boundaries to include keyframes before animation start and after animation length.
+	int track_count = animation->get_track_count();
+	for (int track = 0; track < track_count; ++track) {
+		for (int i = 0; i < animation->track_get_key_count(track); i++) {
+			float key_time = animation->track_get_key_time(track, i);
+			if (key_time > anim_end) {
+				anim_end = key_time;
+			}
+			if (key_time < anim_start) {
+				anim_start = key_time;
+			}
+		}
+	}
+
+	float anim_length = anim_end - anim_start;
+	int timeline_width_pixels = get_size().width - get_buttons_width() - get_name_limit();
+
+	// I want a little buffer at the end... (5% looks nice and we should keep some space for the bezier handles)
+	timeline_width_pixels *= 0.95;
+
+	// The technique is to reuse the _get_zoom_scale function directly to be sure that the auto_fit is always calculated
+	// the same way as the zoom slider. It's a little bit more calculation then doing the inverse of get_zoom_scale but
+	// it's really easier to understand and should always be accurate.
+	float new_zoom = zoom->get_max();
+	while (true) {
+		double test_zoom_scale = _get_zoom_scale(new_zoom);
+
+		if (anim_length * test_zoom_scale <= timeline_width_pixels) {
+			// It fits...
+			break;
+		}
+
+		new_zoom -= zoom->get_step();
+
+		if (new_zoom <= zoom->get_min()) {
+			new_zoom = zoom->get_min();
+			break;
+		}
+	}
+
+	// Horizontal scroll to get_min which should include keyframes that are before the animation start.
+	hscroll->set_value(hscroll->get_min());
+	// Set the zoom value... the signal value_changed will be emitted and the timeline will be refreshed correctly!
+	zoom->set_value(new_zoom);
+	// The new zoom value must be applied correctly so the scrollbar are updated before we move the scrollbar to
+	// the beginning of the animation, hence the call deferred.
+	callable_mp(this, &AnimationTimelineEdit::_scroll_to_start).call_deferred();
+}
+
+void AnimationTimelineEdit::_scroll_to_start() {
+	// Horizontal scroll to get_min which should include keyframes that are before the animation start.
+	hscroll->set_value(hscroll->get_min());
+}
+
 void AnimationTimelineEdit::set_track_edit(AnimationTrackEdit *p_track_edit) {
 	track_edit = p_track_edit;
 }
@@ -3446,6 +3512,8 @@ void AnimationTrackEditor::set_animation(const Ref<Animation> &p_anim, bool p_re
 		step->set_read_only(false);
 		snap->set_disabled(false);
 		snap_mode->set_disabled(false);
+		auto_fit->set_disabled(false);
+		auto_fit_bezier->set_disabled(false);
 
 		imported_anim_warning->hide();
 		for (int i = 0; i < animation->get_track_count(); i++) {
@@ -3466,6 +3534,8 @@ void AnimationTrackEditor::set_animation(const Ref<Animation> &p_anim, bool p_re
 		snap->set_disabled(true);
 		snap_mode->set_disabled(true);
 		bezier_edit_icon->set_disabled(true);
+		auto_fit->set_disabled(true);
+		auto_fit_bezier->set_disabled(true);
 	}
 }
 
@@ -4763,6 +4833,8 @@ void AnimationTrackEditor::_notification(int p_what) {
 			inactive_player_warning->set_icon(get_editor_theme_icon(SNAME("NodeWarning")));
 			main_panel->add_theme_style_override("panel", get_theme_stylebox(SNAME("panel"), SNAME("Tree")));
 			edit->get_popup()->set_item_icon(edit->get_popup()->get_item_index(EDIT_APPLY_RESET), get_editor_theme_icon(SNAME("Reload")));
+			auto_fit->set_icon(get_editor_theme_icon(SNAME("AnimationAutoFit")));
+			auto_fit_bezier->set_icon(get_editor_theme_icon(SNAME("AnimationAutoFitBezier")));
 		} break;
 
 		case NOTIFICATION_READY: {
@@ -5617,6 +5689,8 @@ void AnimationTrackEditor::_cancel_bezier_edit() {
 	bezier_edit->hide();
 	scroll->show();
 	bezier_edit_icon->set_pressed(false);
+	auto_fit->show();
+	auto_fit_bezier->hide();
 }
 
 void AnimationTrackEditor::_bezier_edit(int p_for_track) {
@@ -5625,6 +5699,8 @@ void AnimationTrackEditor::_bezier_edit(int p_for_track) {
 	bezier_edit->set_animation_and_track(animation, p_for_track, read_only);
 	scroll->hide();
 	bezier_edit->show();
+	auto_fit->hide();
+	auto_fit_bezier->show();
 	// Search everything within the track and curve - edit it.
 }
 
@@ -6865,6 +6941,18 @@ bool AnimationTrackEditor::is_grouping_tracks() {
 	return !view_group->is_pressed();
 }
 
+void AnimationTrackEditor::_auto_fit() {
+	timeline->auto_fit();
+}
+
+void AnimationTrackEditor::_auto_fit_bezier() {
+	timeline->auto_fit();
+
+	if (bezier_edit->is_visible()) {
+		bezier_edit->auto_fit_vertically();
+	}
+}
+
 void AnimationTrackEditor::_selection_changed() {
 	if (selected_filter->is_pressed()) {
 		_update_tracks(); // Needs updatin.
@@ -7179,6 +7267,19 @@ AnimationTrackEditor::AnimationTrackEditor() {
 	bottom_hb->add_child(zoom);
 	timeline->set_zoom(zoom);
 
+	auto_fit = memnew(Button);
+	auto_fit->set_flat(true);
+	auto_fit->connect("pressed", callable_mp(this, &AnimationTrackEditor::_auto_fit));
+	auto_fit->set_shortcut(ED_SHORTCUT("animation_editor/auto_fit", TTR("Fit to panel"), KeyModifierMask::ALT | Key::F));
+	bottom_hb->add_child(auto_fit);
+
+	auto_fit_bezier = memnew(Button);
+	auto_fit_bezier->set_flat(true);
+	auto_fit_bezier->set_visible(false);
+	auto_fit_bezier->connect("pressed", callable_mp(this, &AnimationTrackEditor::_auto_fit_bezier));
+	auto_fit_bezier->set_shortcut(ED_SHORTCUT("animation_editor/auto_fit", TTR("Fit to panel"), KeyModifierMask::ALT | Key::F));
+	bottom_hb->add_child(auto_fit_bezier);
+
 	edit = memnew(MenuButton);
 	edit->set_shortcut_context(this);
 	edit->set_text(TTR("Edit"));