statistics: create themes on demand

Create the themes only when needed (singleton pattern). If
the themes should do more than colors, such as for example
fonts, it is not clear whether that can be done before main()
runs. By creating the themes on demand, the Qt UI should
be initialized in the constructors of the themes.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

stats/statscolors.cpp

@@ -1,5 +1,7 @@
 #include "statscolors.h"
 #include "statstranslations.h"
+#include "core/globals.h"
+#include <array>
 
 // Colors created using the Chroma.js Color Palette Helper
 // https://vis4.net/palettes/#/50|d|00108c,3ed8ff,ffffe0|ffffe0,ff005e,743535|1|1
@@ -143,6 +145,16 @@ private:
 	}
 };
 
-static StatsThemeLight statsThemeLight;
+// Currently, we only support two themes: bright and dark.
-static StatsThemeDark statsThemeDark;
+// The themes are generated on first use. Thus, the constructors are run
-std::vector<const StatsTheme *> statsThemes = { &statsThemeLight, &statsThemeDark };
+// once the overall application is initialized. This ensures that the themes'
+// constructors can access the settings, etc.
+static std::array<const StatsTheme *, 2> statsThemes;
+const StatsTheme &getStatsTheme(bool dark)
+{
+	if (!statsThemes[0]) {
+		statsThemes[0] = make_global<StatsThemeLight>();
+		statsThemes[1] = make_global<StatsThemeDark>();
+	}
+	return *statsThemes[dark ? 1 : 0];
+}

stats/statscolors.h

@@ -3,7 +3,7 @@
 #ifndef STATSCOLORS_H
 #define STATSCOLORS_H
 
-#include <vector>
+#include <memory>
 #include <QColor>
 #include <QString>
 
@@ -50,6 +50,6 @@ public:
 	mutable QSGTexture *selectedTexture = nullptr; // A checkerboard pattern.
 };
 
-extern std::vector<const StatsTheme *> statsThemes;
+extern const StatsTheme &getStatsTheme(bool dark);
 
 #endif

stats/statsview.cpp

@@ -35,7 +35,7 @@ static const double selectionLassoWidth = 2.0;		// Border between title and char
 
 StatsView::StatsView(QQuickItem *parent) : QQuickItem(parent),
 	backgroundDirty(true),
-	currentTheme(statsThemes[0]),
+	currentTheme(&getStatsTheme(false)),
 	highlightedSeries(nullptr),
 	xAxis(nullptr),
 	yAxis(nullptr),
@@ -300,10 +300,9 @@ QQuickWindow *StatsView::w() const
 	return window();
 }
 
-void StatsView::setTheme(int idx)
+void StatsView::setTheme(bool dark)
 {
-	idx = std::clamp(idx, 0, (int)statsThemes.size() - 1);
+	currentTheme = &getStatsTheme(dark);
-	currentTheme = statsThemes[idx];
 	rootNode->backgroundNode->setColor(currentTheme->backgroundColor);
 }
 

stats/statsview.h

@@ -54,7 +54,7 @@ public:
 	QQuickWindow *w() const;			// Make window available to items
 	QSizeF size() const;
 	QRectF plotArea() const;
-	void setTheme(int idx);				// Invalid indexes will result in the default theme. Chart must be replot for theme to become effective.
+	void setTheme(bool dark);			// Chart must be replot for theme to become effective.
 	const StatsTheme &getCurrentTheme() const;
 	void addQSGNode(QSGNode *node, ChartZValue z);	// Must only be called in render thread!
 	void registerChartItem(ChartItem &item);