tests: coverage for small utility widgets (66 cases)

- slider: SliderBase/FloatSlider/IntegerSlider mapping, clamping,
  display transforms, drag math, tristate, label substitution
- layouts: FlowLayout wrap math, ColumnedGridLayout placement
- combos: all standard combos, node combo box, color label combo
- misc: menu, file/path fields, toolbar, color button/wheel widgets,
  bezier, resizable scrollbar, hand-movable view, node value tree,
  pixel sampler, collapse button, clickable/focusable labels

tests/gtest/widget_layout_test.cpp

@@ -0,0 +1,119 @@
+#include <gtest/gtest.h>
+
+#include <QPushButton>
+
+#include "widget/columnedgridlayout/columnedgridlayout.h"
+#include "widget/flowlayout/flowlayout.h"
+
+TEST(WidgetLayout, FlowLayoutCountsAndTakesItems)
+{
+	QWidget container;
+	FlowLayout *layout = new FlowLayout(&container, 0, 0, 0);
+
+	auto *a = new QPushButton(QStringLiteral("A"));
+	auto *b = new QPushButton(QStringLiteral("B"));
+	layout->addWidget(a);
+	layout->addWidget(b);
+
+	ASSERT_EQ(layout->count(), 2);
+	EXPECT_EQ(layout->itemAt(0)->widget(), a);
+	EXPECT_EQ(layout->itemAt(1)->widget(), b);
+	EXPECT_EQ(layout->itemAt(2), nullptr);
+
+	QLayoutItem *taken = layout->takeAt(0);
+	ASSERT_NE(taken, nullptr);
+	EXPECT_EQ(taken->widget(), a);
+	EXPECT_EQ(layout->count(), 1);
+	delete taken;
+
+	EXPECT_EQ(layout->takeAt(99), nullptr);
+	EXPECT_EQ(layout->takeAt(-1), nullptr);
+}
+
+TEST(WidgetLayout, FlowLayoutSpacingGetters)
+{
+	QWidget container;
+	FlowLayout *layout = new FlowLayout(&container, 0, 7, 9);
+
+	EXPECT_EQ(layout->horizontalSpacing(), 7);
+	EXPECT_EQ(layout->verticalSpacing(), 9);
+}
+
+TEST(WidgetLayout, FlowLayoutWrapsAndComputesHeightForWidth)
+{
+	QWidget container;
+	FlowLayout *layout = new FlowLayout(&container, 0, 0, 0);
+
+	const int kButtonCount = 5;
+	for (int i = 0; i < kButtonCount; i++) {
+		auto *b = new QPushButton(QStringLiteral("Btn"));
+		b->setFixedSize(100, 30);
+		layout->addWidget(b);
+	}
+
+	EXPECT_TRUE(layout->hasHeightForWidth());
+	EXPECT_EQ(layout->expandingDirections(), Qt::Horizontal | Qt::Vertical);
+
+	// 1000px fits all five 100px buttons on one row; 250px fits two per row,
+	// so five buttons need three rows
+	EXPECT_EQ(layout->heightForWidth(1000), 30);
+	EXPECT_EQ(layout->heightForWidth(250), 90);
+
+	// Lay out for real and inspect positions
+	layout->setGeometry(QRect(0, 0, 250, 90));
+	ASSERT_EQ(layout->count(), kButtonCount);
+
+	EXPECT_EQ(layout->itemAt(0)->geometry().topLeft(), QPoint(0, 0));
+	EXPECT_EQ(layout->itemAt(1)->geometry().topLeft(), QPoint(100, 0));
+
+	// Third button wraps to the second row, fifth to the third
+	EXPECT_EQ(layout->itemAt(2)->geometry().topLeft(), QPoint(0, 30));
+	EXPECT_EQ(layout->itemAt(4)->geometry().topLeft(), QPoint(0, 60));
+
+	EXPECT_TRUE(layout->sizeHint().isValid());
+}
+
+TEST(WidgetLayout, ColumnedGridLayoutArrangesByMaximumColumns)
+{
+	QWidget container;
+	olive::ColumnedGridLayout *layout =
+		new olive::ColumnedGridLayout(&container, 3);
+
+	QVector<QPushButton *> buttons;
+	for (int i = 0; i < 7; i++) {
+		auto *b = new QPushButton(QString::number(i));
+		buttons.append(b);
+		layout->Add(b);
+	}
+
+	EXPECT_EQ(layout->MaximumColumns(), 3);
+	EXPECT_EQ(layout->count(), 7);
+
+	// Widgets are placed row-major with at most three columns
+	for (int i = 0; i < buttons.size(); i++) {
+		QLayoutItem *item = layout->itemAtPosition(i / 3, i % 3);
+		ASSERT_NE(item, nullptr) << i;
+		EXPECT_EQ(item->widget(), buttons.at(i)) << i;
+	}
+
+	// Nothing beyond the last populated cell
+	EXPECT_EQ(layout->itemAtPosition(2, 1), nullptr);
+
+	layout->SetMaximumColumns(4);
+	EXPECT_EQ(layout->MaximumColumns(), 4);
+}
+
+TEST(WidgetLayout, ColumnedGridLayoutWithoutColumnLimitStillAdds)
+{
+	QWidget container;
+	olive::ColumnedGridLayout *layout = new olive::ColumnedGridLayout(&container);
+
+	EXPECT_EQ(layout->MaximumColumns(), 0);
+
+	auto *a = new QPushButton(QStringLiteral("A"));
+	auto *b = new QPushButton(QStringLiteral("B"));
+	layout->Add(a);
+	layout->Add(b);
+
+	EXPECT_EQ(layout->count(), 2);
+}