debug: add lint for zero sized items

src/CMakeLists.txt

@@ -5,6 +5,7 @@ install(TARGETS quickshell RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 add_subdirectory(build)
 add_subdirectory(launch)
 add_subdirectory(core)
+add_subdirectory(debug)
 add_subdirectory(ipc)
 add_subdirectory(window)
 add_subdirectory(io)

src/debug/CMakeLists.txt

@@ -0,0 +1,7 @@
+qt_add_library(quickshell-debug STATIC
+	lint.cpp
+)
+
+qs_pch(quickshell-debug)
+target_link_libraries(quickshell-debug PRIVATE Qt::Quick)
+target_link_libraries(quickshell PRIVATE quickshell-debug)

src/debug/lint.cpp

@@ -0,0 +1,81 @@
+#include "lint.hpp"
+#include <algorithm>
+
+#include <qlogging.h>
+#include <qloggingcategory.h>
+#include <qobject.h>
+#include <qqmlcontext.h>
+#include <qqmlengine.h>
+#include <qqmlinfo.h>
+#include <qquickframebufferobject.h>
+#include <qquickitem.h>
+#include <qquickpainteditem.h>
+#include <qquickrhiitem.h>
+#include <qquickwindow.h>
+#include <qstringliteral.h>
+
+namespace qs::debug {
+
+Q_LOGGING_CATEGORY(logLint, "quickshell.linter", QtWarningMsg);
+
+void lintZeroSized(QQuickItem* item);
+bool isRenderable(QQuickItem* item);
+
+void lintObjectTree(QObject* object) {
+	if (!logLint().isWarningEnabled()) return;
+
+	qCDebug(logLint) << "Walking children of object" << object;
+
+	for (auto* child: object->children()) {
+		if (child->isQuickItemType()) {
+			auto* item = static_cast<QQuickItem*>(child); // NOLINT;
+			lintItemTree(item);
+		} else {
+			lintObjectTree(child);
+		}
+	}
+}
+
+void lintItemTree(QQuickItem* item) {
+	if (!logLint().isWarningEnabled()) return;
+
+	qCDebug(logLint) << "Running lints for item" << item;
+	lintZeroSized(item);
+
+	qCDebug(logLint) << "Walking visual children of item" << item;
+	for (auto* child: item->childItems()) {
+		lintItemTree(child);
+	}
+}
+
+void lintZeroSized(QQuickItem* item) {
+	if (!item->isEnabled() || !item->isVisible()) return;
+	if (item->childItems().isEmpty()) return;
+
+	auto zeroWidth = item->width() == 0;
+	auto zeroHeight = item->height() == 0;
+
+	if (!zeroWidth && !zeroHeight) return;
+
+	if (!isRenderable(item)) return;
+
+	auto* ctx = QQmlEngine::contextForObject(item);
+	if (!ctx || ctx->baseUrl().scheme() != QStringLiteral("qsintercept")) return;
+
+	qmlWarning(item) << "Item is visible and has visible children, but has zero "
+	                 << (zeroWidth && zeroHeight ? "width and height"
+	                     : zeroWidth             ? "width"
+	                                             : "height");
+}
+
+bool isRenderable(QQuickItem* item) {
+	if (!item->isEnabled() || !item->isVisible()) return false;
+
+	if (item->flags().testFlags(QQuickItem::ItemHasContents)) {
+		return true;
+	}
+
+	return std::ranges::any_of(item->childItems(), [](auto* item) { return isRenderable(item); });
+}
+
+} // namespace qs::debug

src/debug/lint.hpp

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <qobject.h>
+#include <qquickitem.h>
+
+namespace qs::debug {
+
+void lintObjectTree(QObject* object);
+void lintItemTree(QQuickItem* item);
+
+} // namespace qs::debug

src/window/CMakeLists.txt

@@ -22,6 +22,8 @@ target_link_libraries(quickshell-window PRIVATE
 	Qt::Core Qt::Gui Qt::Quick Qt6::QuickPrivate
 )
 
+qs_add_link_dependencies(quickshell-window quickshell-debug)
+
 target_link_libraries(quickshell-window-init PRIVATE Qt::Qml)
 
 qs_module_pch(quickshell-window SET large)

src/window/proxywindow.cpp

@@ -19,6 +19,7 @@
 #include "../core/qmlscreen.hpp"
 #include "../core/region.hpp"
 #include "../core/reload.hpp"
+#include "../debug/lint.hpp"
 #include "windowinterface.hpp"
 
 ProxyWindowBase::ProxyWindowBase(QObject* parent)
@@ -214,6 +215,11 @@ void ProxyWindowBase::polishItems() {
 	// This hack manually polishes the item tree right before showing the window so it will
 	// always be created with the correct size.
 	QQuickWindowPrivate::get(this->window)->polishItems();
+
+	if (!this->ranLints) {
+		qs::debug::lintItemTree(this->mContentItem);
+		this->ranLints = true;
+	}
 }
 
 qint32 ProxyWindowBase::x() const {

src/window/proxywindow.hpp

@@ -130,6 +130,7 @@ protected:
 	QQuickWindow* window = nullptr;
 	QQuickItem* mContentItem = nullptr;
 	bool reloadComplete = false;
+	bool ranLints = false;
 
 private:
 	void polishItems();