Started a histogram example.

examples/histogram/GNUmakefile

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+# 2 september 2015
+
+OUT = histogram
+
+ifeq ($(OS),windows)
+linkto = ../../out/new.dll
+CC = i686-w64-mingw32-gcc
+OUT = controlgallery.exe
+else
+ifeq ($(OS),darwin)
+linkto = ../../out/new.dylib
+else
+linkto = ../../out/new.so
+endif
+endif
+
+CFILES = \
+	main.c
+
+OFILES = $(CFILES:%.c=%.o)
+
+controlgallery: $(OFILES)
+	$(CC) -g -o $(OUT) $(OFILES) $(linkto)
+
+%.o: %.c
+	$(CC) -c -g -o $@ $<
+
+clean:
+	rm -f $(OUT) $(OFILES)

examples/histogram/main.c

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+// 13 october 2015
+#include <stdio.h>
+#include <string.h>
+#include "../../ui.h"
+
+uiWindow *mainwin;
+uiArea *histogram;
+uiAreaHandler handler;
+uiSpinbox *datapoints[10];
+
+// some metrics
+#define xoffLeft 20			/* histogram margins */
+#define yoffTop 20
+#define xoffRight 20
+#define yoffBottom 20
+
+// helper to quickly set a brush color
+static void setSolidBrush(uiDrawBrush *brush, uint32_t color, double alpha)
+{
+	uint8_t component;
+
+	brush->Type = uiDrawBrushTypeSolid;
+	component = (uint8_t) ((color >> 16) & 0xFF);
+	brush->R = ((double) component) / 255;
+	component = (uint8_t) ((color >> 8) & 0xFF);
+	brush->G = ((double) component) / 255;
+	component = (uint8_t) (color & 0xFF);
+	brush->B = ((double) component) / 255;
+	brush->A = alpha;
+}
+
+// and some colors
+// names and values from https://msdn.microsoft.com/en-us/library/windows/desktop/dd370907%28v=vs.85%29.aspx
+#define colorWhite 0xFFFFFF
+#define colorBlack 0x000000
+#define colorDodgerBlue 0x1E90FF
+
+static uiDrawPath *constructGraph(double width, double height, int extend)
+{
+	uiDrawPath *path;
+	double xincr, yincr;
+	int i, n;
+
+	path = uiDrawNewPath(uiDrawFillModeWinding);
+
+	xincr = width / 9;		// 10 - 1 to make the last point be at the end
+	yincr = height / 100;
+	for (i = 0; i < 10; i++) {
+		// get the value of the point
+		n = uiSpinboxValue(datapoints[i]);
+		// because y=0 is the top but n=0 is the bottom, we need to flip
+		n = 100 - n;
+		if (i == 0)
+			uiDrawPathNewFigure(path,
+				xincr * i,
+				yincr * n);
+		else
+			uiDrawPathLineTo(path,
+				xincr * i,
+				yincr * n);
+	}
+
+	if (extend) {
+		uiDrawPathLineTo(path, width, height);
+		uiDrawPathLineTo(path, 0, height);
+		uiDrawPathCloseFigure(path);
+	}
+
+	uiDrawPathEnd(path);
+	return path;
+}
+
+static void handlerDraw(uiAreaHandler *a, uiArea *area, uiAreaDrawParams *p)
+{
+	uiDrawPath *path;
+	uiDrawBrush brush;
+	uiDrawStrokeParams sp;
+	uiDrawMatrix m;
+	double graphWidth, graphHeight;
+
+	// fill the area with white
+	setSolidBrush(&brush, colorWhite, 1.0);
+	path = uiDrawNewPath(uiDrawFillModeWinding);
+	uiDrawPathAddRectangle(path, 0, 0, p->ClientWidth, p->ClientHeight);
+	uiDrawPathEnd(path);
+	uiDrawFill(p->Context, path, &brush);
+	uiDrawFreePath(path);
+
+	// figure out dimensions
+	graphWidth = p->ClientWidth - xoffLeft - xoffRight;
+	graphHeight = p->ClientHeight - yoffTop - yoffBottom;
+
+	// draw the axes
+	setSolidBrush(&brush, colorBlack, 1.0);
+	path = uiDrawNewPath(uiDrawFillModeWinding);
+	uiDrawPathNewFigure(path,
+		xoffLeft, yoffTop);
+	uiDrawPathLineTo(path,
+		xoffLeft, yoffTop + graphHeight);
+	uiDrawPathLineTo(path,
+		xoffLeft + graphWidth, yoffTop + graphHeight);
+	uiDrawPathEnd(path);
+	sp.Cap = uiDrawLineCapFlat;
+	sp.Join = uiDrawLineJoinMiter;
+	sp.Thickness = 2;
+	sp.MiterLimit = uiDrawDefaultMiterLimit;
+	uiDrawStroke(p->Context, path, &brush, &sp);
+	uiDrawFreePath(path);
+
+	// now transform the coordinate space so (0, 0) is the top-left corner of the graph
+	uiDrawMatrixSetIdentity(&m);
+	uiDrawMatrixTranslate(&m, xoffLeft, yoffTop);
+	uiDrawTransform(p->Context, &m);
+
+	// now create the fill for the graph below the graph line
+	path = constructGraph(graphWidth, graphHeight, 1);
+	setSolidBrush(&brush, colorDodgerBlue, 0.5);
+	uiDrawFill(p->Context, path, &brush);
+	uiDrawFreePath(path);
+}
+
+static uintmax_t handlerHScrollMax(uiAreaHandler *a, uiArea *area)
+{
+	return 0;
+}
+
+static uintmax_t handlerVScrollMax(uiAreaHandler *a, uiArea *area)
+{
+	return 0;
+}
+
+static int handlerRedrawOnResize(uiAreaHandler *a, uiArea *area)
+{
+	return 1;
+}
+
+static void handlerMouseEvent(uiAreaHandler *a, uiArea *area, uiAreaMouseEvent *e)
+{
+	// do nothing
+}
+
+static void handlerDragBroken(uiAreaHandler *ah, uiArea *a)
+{
+	// do nothing
+}
+
+static int handlerKeyEvent(uiAreaHandler *ah, uiArea *a, uiAreaKeyEvent *e)
+{
+	return 0;
+}
+
+static int onClosing(uiWindow *w, void *data)
+{
+	uiControlDestroy(uiControl(mainwin));
+	uiQuit();
+	return 0;
+}
+
+static int shouldQuit(void *data)
+{
+	uiControlDestroy(uiControl(mainwin));
+	return 1;
+}
+
+int main(void)
+{
+	uiInitOptions o;
+	const char *err;
+	uiBox *hbox, *vbox;
+	int i;
+
+	handler.Draw = handlerDraw;
+	handler.HScrollMax = handlerHScrollMax;
+	handler.VScrollMax = handlerVScrollMax;
+	handler.RedrawOnResize = handlerRedrawOnResize;
+	handler.MouseEvent = handlerMouseEvent;
+	handler.DragBroken = handlerDragBroken;
+	handler.KeyEvent = handlerKeyEvent;
+
+	memset(&o, 0, sizeof (uiInitOptions));
+	err = uiInit(&o);
+	if (err != NULL) {
+		fprintf(stderr, "error initializing ui: %s\n", err);
+		uiFreeInitError(err);
+		return 1;
+	}
+
+	uiOnShouldQuit(shouldQuit, NULL);
+
+	mainwin = uiNewWindow("libui Histogram Example", 640, 480, 1);
+	uiWindowSetMargined(mainwin, 1);
+	uiWindowOnClosing(mainwin, onClosing, NULL);
+
+	hbox = uiNewHorizontalBox();
+	uiBoxSetPadded(hbox, 1);
+	uiWindowSetChild(mainwin, uiControl(hbox));
+
+	vbox = uiNewVerticalBox();
+	uiBoxSetPadded(vbox, 1);
+	uiBoxAppend(hbox, uiControl(vbox), 0);
+
+	for (i = 0; i < 10; i++) {
+		datapoints[i] = uiNewSpinbox(0, 100);
+		uiBoxAppend(vbox, uiControl(datapoints[i]), 0);
+	}
+
+	histogram = uiNewArea(&handler);
+	uiBoxAppend(hbox, uiControl(histogram), 1);
+
+	uiControlShow(uiControl(mainwin));
+	uiMain();
+	uiUninit();
+	return 0;
+}