fosphor/gl: Add a proper "smart" frequency axis

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

lib/fosphor/Makefile

@@ -20,7 +20,7 @@ all: main
 resource_data.c: $(RESOURCE_FILES) mkresources.py
 	./mkresources.py $(RESOURCE_FILES) > resource_data.c
 
-main: resource.o resource_data.o cl.o fosphor.o gl.o gl_cmap.o gl_cmap_gen.o gl_font.o main.o
+main: resource.o resource_data.o axis.o cl.o fosphor.o gl.o gl_cmap.o gl_cmap_gen.o gl_font.o main.o
 
 clean:
 	rm main *.o resource_data.c -f

lib/fosphor/axis.c

@@ -0,0 +1,170 @@
+/*
+ * axis.c
+ *
+ * Logic to deal with various axises
+ *
+ * Copyright (C) 2013 Sylvain Munaut
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*! \addtogroup axis
+ *  @{
+ */
+
+/*! \file axis.c
+ *  \brief Logic to deal with various axises
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#include "axis.h"
+
+
+#define FX_MODE_COUNT		0
+#define FX_MODE_RELATIVE	1
+#define FX_MODE_ABSOLUTE	2
+
+
+static double
+_si_scaling(double val, int max_num, char *prefix, int *exp)
+{
+	const char prefixes[5] = { ' ', 'k', 'M', 'G', 'T' };
+	int exponent = log10f(fabs(val));
+	int d = exponent >= max_num ? ((exponent - max_num + 3) / 3) : 0;
+
+	if (prefix)
+		*prefix = prefixes[d];
+
+	if (exp)
+		*exp = d * 3;
+
+	return val / powf(10.0, d * 3);
+}
+
+static int
+_num_decimals(double val)
+{
+	int c;
+	double v;
+
+	for (c=0; c<22; c++) {
+		v = val * pow(10, c);
+		if ( fabs(v - round(v)) == 0.0 )
+			return c;
+	}
+
+	return -1;
+}
+
+
+void
+freq_axis_build(struct freq_axis *fx, double center, double span)
+{
+	/* Basic info */
+	fx->center = center;
+	fx->span   = span;
+	fx->step   = span / 10.0;
+
+	/* Select mode of operation */
+	if (span == 0.0) {
+		fx->mode = FX_MODE_COUNT;
+	} else if (center == 0.0) {
+		fx->mode = FX_MODE_RELATIVE;
+	} else if (floor(log10f(fx->step)) < (floor(log10f(fx->center)) - 4)) {
+		fx->mode = FX_MODE_RELATIVE;
+	} else {
+		fx->mode = FX_MODE_ABSOLUTE;
+	}
+
+	/* Select display format for abolute frequencies */
+	if (center != 0.0)
+	{
+		double max_freq = fx->center + (span / 2.0);
+		char prefix[2] = {0, 0};
+		int exp, x, y, z;
+
+		_si_scaling(max_freq, 4, prefix, &exp);
+
+		if (prefix[0] == ' ')
+			prefix[0] = '\0';
+
+		fx->abs_scale = 1.0 / powf(10.0, exp);
+
+		x = (int)floor(log10f(max_freq)) - exp + 1;
+		y = _num_decimals(fx->center * fx->abs_scale);
+		z = _num_decimals(fx->step   * fx->abs_scale);
+
+		if (z > y)
+			y = z;
+
+		if (x + y > 6)
+			y = 6 - x;
+
+		sprintf(fx->abs_fmt, "%%.%dlf%s", y, prefix);
+	}
+
+	/* Select display format for relative mode */
+	if (fx->mode == FX_MODE_RELATIVE)
+	{
+		double max_dev = fx->step * 5;
+		char prefix[2] = {0, 0};
+		int exp, x, y;
+
+		_si_scaling(max_dev, 3, prefix, &exp);
+
+		if (prefix[0] == ' ')
+			prefix[0] = '\0';
+
+		fx->rel_step = fx->step / powf(10.0, exp);
+
+		x = (int)floor(log10f(max_dev)) - exp + 1;
+		y = _num_decimals(fx->rel_step);
+
+		if (x + y > 4)
+			y = 4 - x;
+
+		sprintf(fx->rel_fmt, "%%+.%dlf%s", y, prefix);
+	}
+}
+
+void
+freq_axis_render(struct freq_axis *fx, char *str, int step)
+{
+	/* Special case: count mode */
+	if (step && (fx->mode == FX_MODE_COUNT)) {
+		sprintf(str, "%+d", step);
+		return;
+	}
+
+	/* Special case: no center frequency */
+	if (!step && (fx->center == 0.0)) {
+		sprintf(str, "0");
+		return;
+	}
+
+	/* Relative case */
+	if (step && (fx->mode == FX_MODE_RELATIVE)) {
+		sprintf(str, fx->rel_fmt, step * fx->rel_step);
+		return;
+	}
+
+	/* Normal full absolute frequency */
+	sprintf(str, fx->abs_fmt, (fx->center + step * fx->step) * fx->abs_scale);
+}
+
+/*! @} */

lib/fosphor/axis.h

@@ -0,0 +1,50 @@
+/*
+ * axis.h
+ *
+ * Logic to deal with various axises
+ *
+ * Copyright (C) 2013 Sylvain Munaut
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __FOSPHOR_AXIS_H__
+#define __FOSPHOR_AXIS_H__
+
+/*! \defgroup axis
+ *  @{
+ */
+
+/*! \file axis.h
+ *  \brief Logic to deal with various axises
+ */
+
+struct freq_axis
+{
+	double center;
+	double span;
+	double step;
+	int    mode;
+	char   abs_fmt[16];
+	double abs_scale;
+	char   rel_fmt[16];
+	double rel_step;
+};
+
+void freq_axis_build(struct freq_axis *fx, double center, double span);
+void freq_axis_render(struct freq_axis *fx, char *str, int step);
+
+/*! @} */
+
+#endif /* __FOSPHOR_AXIS_H__ */

lib/fosphor/gl.c

@@ -28,12 +28,14 @@
  */
 
 #include <errno.h>
+#include <math.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 
 #include "gl_platform.h"
 
+#include "axis.h"
 #include "gl.h"
 #include "gl_cmap.h"
 #include "gl_cmap_gen.h"
@@ -284,6 +286,7 @@ void
 fosphor_gl_draw(struct fosphor *self, int w, int h, int wf_pos)
 {
 	struct fosphor_gl_state *gl = self->gl;
+	struct freq_axis freq_axis;
 	float x_div_width, y_div_width;
 	float x[2], y[4];
 	int i;
@@ -365,11 +368,18 @@ fosphor_gl_draw(struct fosphor *self, int w, int h, int wf_pos)
 
         glPopMatrix();
 
+	/* Setup frequency axis */
+	freq_axis_build(&freq_axis,
+	                self->frequency.center,
+	                self->frequency.span
+	);
+
 	/* Draw grid */
 	for (i=0; i<11; i++)
 	{
 		float fg_color[3] = { 1.00f, 1.00f, 0.33f };
-		float xv, yv;
+		float xv, yv, xv_ofs;
+		char buf[32];
 
 		xv = x[0] + x_div_width * i;
 		yv = y[2] + y_div_width * i;
@@ -398,10 +408,14 @@ fosphor_gl_draw(struct fosphor *self, int w, int h, int wf_pos)
 		           "%d", self->power.db_ref - (10-i) * self->power.db_per_div
 		);
 
+		freq_axis_render(&freq_axis, buf, i-5);
+
+		xv_ofs = (i == 0) ? 5.0f : (i == 10 ? -5.0f : 0.0f);
+
 		glf_printf(gl->font,
-		           xv - 5.0f, GLF_CENTER,
-		           y[2] - 10.0f, GLF_CENTER,
-		           "%3d", (i - 5)
+			   xv + xv_ofs, GLF_CENTER,
+			   y[2] - 10.0f, GLF_CENTER,
+			   "%s", buf
 		);
 
 		glf_end();