Designer: deal the section settings out into four tabs

ARCHITECTURE.md

@@ -1181,18 +1181,53 @@ taking a type apart is a property of the type table rather than of this window,
 mapping that has to be exactly reversible is worth a test that needs no window on screen. Nothing
 about persistence changes: the document still carries all twenty ids.
 
-**The rows are gathered into named groups that fold away** — *Content Properties*, the type's own
-settings, *Layout Properties* — with the middle one titled after the type in it, since
-"Bridge settings" and "Divider settings" are never on screen at once. A `CollapsibleGroup` rather
-than a checkable `QGroupBox`: a checkbox on a group reads as switching the group *off*, which is
-what the checkable groups already in this editor mean. A group whose every row is hidden goes away
-with them, which is asked of the layout rather than of the widgets in it — a child of a window that
-has not been shown yet reads as hidden whether or not anything hid it.
+**The settings are dealt out into four tabs rather than stacked in one column** — *Content*,
+*Layout*, *Style*, *Background* (`EditorTab`). Fifteen groups one under the next was everything
+about a section at once in a pane a third of a window wide; folding the groups away made the column
+shorter without making it any less of a column, and somebody working on the words still scrolled
+past the geometry to reach them. The four are the jobs somebody sits down to do — fill the section
+in, place it, ink it, put something behind it — and each is a whole answer on its own. The document
+is untouched by this: a tab is where a control is drawn and nothing else.
+
+*Content* holds what the section says, and the tables it says it through: the entry table for a
+list, the divider's three piece stacks for a divider (a divider has no words, so those stacks *are*
+its content, and its Content tab holds them alone). *Layout* holds the type's own settings and the
+placement rows. *Style* holds the up-to-five `StyleEditor`s. *Background* holds the eight panel
+slots.
+
+**The type picker, the label, the visible box and the advanced switch stay above the tab strip.**
+They are not settings of any one job: the type decides what every tab holds, the name is how the
+section is found again in the list, and the advanced switch reaches rows on three of the four
+pages. A reader who had to leave the tab they were working in to flip one of them would lose their
+place to change something that governs all of them.
+
+**Each tab scrolls on its own**, so the header and the strip cannot be scrolled off the top and
+each page keeps the place it was left at — going back to *Style* should be going back to where you
+were in it. That is why the designer adds the editor straight to the splitter rather than wrapping
+it in a `QScrollArea` as it used to: the scrolling moved inside, one area per page.
+
+**A tab with nothing on it goes away.** A Spacer has no words, no styles and no panels, so three of
+the four would otherwise be empty panes inviting the reader to look for settings that are not
+there. Asked of the groups on each page rather than of the section type — `applyTypeVisibility` has
+just settled what applies, and counting what it left on screen cannot disagree with it the way a
+second list of conditions could. It asks `isHidden` rather than `isVisible`, because the page of a
+tab nobody is looking at is itself hidden and everything on it would otherwise answer no. The tab
+the reader chose is remembered rather than forced: a tab going away under them takes the selection
+with it, and `desiredTab` is what brings them back to it once the next section has one again, while
+`restoringTab` keeps that shuffle from being read as a choice of theirs.
+
+**Within a tab the rows are still gathered into named groups that fold away** — *Content
+Properties*, the type's own settings, *Placement on the Canvas* — with the middle one titled after
+the type in it, since "Bridge settings" and "Divider settings" are never on screen at once. A
+`CollapsibleGroup` rather than a checkable `QGroupBox`: a checkbox on a group reads as switching the
+group *off*, which is what the checkable groups already in this editor mean. A group whose every row
+is hidden goes away with them, which is asked of the layout rather than of the widgets in it — a
+child of a window that has not been shown yet reads as hidden whether or not anything hid it.
 
 **The style groups fold away too, and the two that switch off carry both controls in one header.**
 A `StyleEditor` is the tallest thing in the pane — a font, a size, a fill with its stops, an
-outline, a shadow, an alignment — and a bridged row with subtitles stacks five of them between the
-placement rows and the entry table, which is the scroll the folding groups were added to end. So
+outline, a shadow, an alignment — and a bridged row with subtitles stacks five of them one under the
+next, which is the length that made the editor feel endless before they had a tab of their own. So
 `CollapsibleGroup` grew the checkbox it was originally written to avoid: it sits *beside* the
 title rather than replacing the disclosure triangle, and the two readings stay apart — the checkbox
 says whether the style applies, the triangle says whether it is on screen, and neither moves the
@@ -1215,11 +1250,12 @@ bridged row's *subtitles* switch adds and takes away, so the editor remembers th
 was built with (`tableType`, `tableRowSubtitles`) and reads through that rather than through the
 switch: the same cell means a different field on each side of the rebuild, and reading a two-column
 table as a four-column one put every row's right-hand name into the left-hand subtitle the moment
-subtitles were switched on. A trailing spacer takes whatever height
-is left over: a `QVBoxLayout` with nothing to give its slack to shares it out between the items
-it has, which spread a short type's handful of rows down the pane with gaps between them. The
-entry table is the one thing worth growing, so it takes the slack instead whenever the selected
-type has one, and asks for enough height to read a run of entries at a glance.
+subtitles were switched on. Each tab's page ends in a trailing spacer that takes whatever height is
+left over: a `QVBoxLayout` with nothing to give its slack to shares it out between the items it
+has, which spread a short type's handful of rows down the page with gaps between them. Whichever
+table the *Content* page is showing is the one thing on it worth growing, so it takes that page's
+slack instead whenever the selected type has one, and asks for enough height to read a run of
+entries at a glance.
 
 **A sticky block's children are branches off it, and fold away.** The list stays a `QListWidget`:
 a roll is a run of sections with one shallow exception in it, and a tree would trade the

data/locale/en-US.ini

@@ -85,9 +85,13 @@ Designer.ListContent.Pairs="A line and a smaller one under it"
 Designer.ListContent.Logos="Images"
 Designer.ShowAdvanced="Show every setting"
 Designer.ShowAdvanced.Tip="Reveals the settings that are rarely needed — where the section sits on the canvas, the fine spacing of a divider, the ordering of a pair. Nothing is switched off while they are hidden."
+Designer.Tab.Content="Content"
+Designer.Tab.Layout="Layout"
+Designer.Tab.Style="Style"
+Designer.Tab.Background="Background"
 Designer.Group.Content="Content Properties"
 Designer.Group.TypeSettings="%1 Settings"
-Designer.Group.Placement="Layout Properties"
+Designer.Group.Placement="Placement on the Canvas"
 Designer.TypeHelp.title="The largest heading. One line, on its own."
 Designer.TypeHelp.title_with_subtitle="A large heading with a second, smaller line under it."
 Designer.TypeHelp.title_with_logo="A large heading with an image beside it."

src/ui/DesignerDialog.cpp

@@ -39,7 +39,6 @@ with this program. If not, see <https://www.gnu.org/licenses/>
 #include <QMenu>
 #include <QMessageBox>
 #include <QPushButton>
-#include <QScrollArea>
 #include <QSignalBlocker>
 #include <QSplitter>
 #include <QTimer>
@@ -464,12 +463,15 @@ DesignerDialog::DesignerDialog(obs_source_t *source, QWidget *parent) : QDialog(
 
 	splitter->addWidget(listPane);
 
-	/* --- middle: the editor for whichever section is selected --- */
-	editorScroll = new QScrollArea(splitter);
-	editorScroll->setWidgetResizable(true);
-	editor = new SectionEditor(editorScroll);
-	editorScroll->setWidget(editor);
-	splitter->addWidget(editorScroll);
+	/*
+	 * --- middle: the editor for whichever section is selected ---
+	 *
+	 * Added straight to the splitter rather than wrapped in a scroll area: the editor is tabbed
+	 * and scrolls each of its pages itself, which is what keeps its type picker and its tab strip
+	 * on screen while a long page is scrolled. See SectionEditor::addTab.
+	 */
+	editor = new SectionEditor(splitter);
+	splitter->addWidget(editor);
 
 	/* --- right: live preview of the whole strip --- */
 	previewPane = new QWidget(splitter);
@@ -986,7 +988,7 @@ void DesignerDialog::refreshSectionList(int selectRow)
 	if (const Section *section = sectionAt(currentPath))
 		editor->setSection(*section);
 
-	editorScroll->setEnabled(row >= 0);
+	editor->setEnabled(row >= 0);
 }
 
 DesignerDialog::DocumentSnapshot DesignerDialog::snapshot() const
@@ -1128,8 +1130,8 @@ void DesignerDialog::setPaneFolded(QWidget *pane, QToolButton *button, int *reme
 	pane->setMaximumWidth(QWIDGETSIZE_MAX);
 
 	const int width = *rememberedWidth > 0 ? *rememberedWidth : kDefaultPaneSizes.value(index);
-	const int editor = splitter->indexOf(editorScroll);
-	if (index == editor || editor < 0 || sizes.size() != splitter->count()) {
+	const int editorIndex = splitter->indexOf(editor);
+	if (index == editorIndex || editorIndex < 0 || sizes.size() != splitter->count()) {
 		splitter->setSizes(kDefaultPaneSizes);
 		return;
 	}
@@ -1139,7 +1141,7 @@ void DesignerDialog::setPaneFolded(QWidget *pane, QToolButton *button, int *reme
 	 * where the user last put it. The editor is the pane with room to spare -- and never let
 	 * below nothing, which the splitter would only hand back at the next resize anyway.
 	 */
-	sizes[editor] = std::max(0, sizes.value(editor) - (width - sizes.value(index)));
+	sizes[editorIndex] = std::max(0, sizes.value(editorIndex) - (width - sizes.value(index)));
 	sizes[index] = width;
 	splitter->setSizes(sizes);
 }
@@ -1161,7 +1163,7 @@ void DesignerDialog::onSelectionChanged()
 	const int row = sectionList->currentRow();
 	currentRow = row;
 	currentPath = row >= 0 && row < rowPaths.size() ? rowPaths.at(row) : SectionPath{};
-	editorScroll->setEnabled(row >= 0);
+	editor->setEnabled(row >= 0);
 	preview->setHighlightedSection(currentPath.isValid() ? highlightFor(currentPath) : -1);
 
 	if (const Section *section = sectionAt(currentPath))

src/ui/DesignerDialog.hpp

@@ -35,7 +35,6 @@ class QDialogButtonBox;
 class QFileSystemWatcher;
 class QLabel;
 class QPushButton;
-class QScrollArea;
 class QSplitter;
 class QTimer;
 class QToolButton;
@@ -377,7 +376,6 @@ class DesignerDialog : public QDialog {
 	int listExpandedWidth = 0;
 
 	SectionEditor *editor = nullptr;
-	QScrollArea *editorScroll = nullptr;
 	PreviewWidget *preview = nullptr;
 	QWidget *previewPane = nullptr;
 	QLabel *previewLabel = nullptr;