Re: [PATCH 1/4] kernel-shark: Add support for drawing text

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

On 5.12.20 г. 1:31 ч., Steven Rostedt wrote:
> On Fri, 20 Nov 2020 11:50:28 +0200
> "Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:
> 
>> OpenGL doesn't provide support for text rendering. Here we first
>> re-enable the compilation of the OpenGL wrapper and add the capability
>> of printing text to the OpenGL scene by using the single-file public
>> domain library "stb_truetype":
>> https://github.com/nothings/stb/blob/master/stb_truetype.h
>>
>> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
>> ---
>>   CMakeLists.txt                   |    6 +-
>>   Documentation/doxygen/dox_config |    1 +
>>   src/CMakeLists.txt               |    4 +-
>>   src/libkshark-plot.c             |  244 +-
>>   src/libkshark-plot.h             |   57 +
>>   src/stb_truetype.h               | 5011 ++++++++++++++++++++++++++++++
>>   6 files changed, 5312 insertions(+), 11 deletions(-)
>>   create mode 100644 src/stb_truetype.h
>>
>> diff --git a/CMakeLists.txt b/CMakeLists.txt
>> index ccca95c1..3d179778 100644
>> --- a/CMakeLists.txt
>> +++ b/CMakeLists.txt
>> @@ -26,9 +26,9 @@ include(${KS_DIR}/build/FindJSONC.cmake)
>>   
>>   find_package(Doxygen)
>>   
>> -# set(OpenGL_GL_PREFERENCE LEGACY)
>> -# find_package(OpenGL)
>> -# find_package(GLUT)
>> +set(OpenGL_GL_PREFERENCE LEGACY)
>> +find_package(OpenGL)
>> +find_package(GLUT)
>>   
>>   # find_package(Qt5Widgets 5.7.1)
>>   # find_package(Qt5Network)
>> diff --git a/Documentation/doxygen/dox_config b/Documentation/doxygen/dox_config
>> index 89b92842..0bbeb3f0 100644
>> --- a/Documentation/doxygen/dox_config
>> +++ b/Documentation/doxygen/dox_config
>> @@ -14,3 +14,4 @@ SORT_MEMBER_DOCS       = NO
>>   STRICT_PROTO_MATCHING  = YES
>>   DOT_MULTI_TARGETS      = YES
>>   PROJECT_LOGO           = ../../icons/KS_logo_stacked.svg
>> +EXCLUDE                = ../../src/stb_truetype.h
>> diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
>> index ae5de54d..3a07d824 100644
>> --- a/src/CMakeLists.txt
>> +++ b/src/CMakeLists.txt
>> @@ -22,8 +22,8 @@ install(TARGETS kshark LIBRARY DESTINATION ${_LIBDIR}/${KS_APP_NAME})
>>   if (OPENGL_FOUND AND GLUT_FOUND)
>>   
>>       message(STATUS "libkshark-plot")
>> -    add_library(kshark-plot  SHARED  libkshark-plot.c
>> -                                     KsPlotTools.cpp)
>> +    add_library(kshark-plot  SHARED  libkshark-plot.c)
>> +#                                      KsPlotTools.cpp)
>>   
>>       target_link_libraries(kshark-plot  kshark
>>                                          ${GLUT_LIBRARY}
>> diff --git a/src/libkshark-plot.c b/src/libkshark-plot.c
>> index 17d3b903..06483334 100644
>> --- a/src/libkshark-plot.c
>> +++ b/src/libkshark-plot.c
>> @@ -1,13 +1,22 @@
>>   /* SPDX-License-Identifier: LGPL-2.1 */
>>   
>>   /*
>> - * Copyright (C) 2018 VMware Inc, Yordan Karadzhov <y.karadz@gmail.com>
>> + * Copyright (C) 2018 VMware Inc, Yordan Karadzhov (VMware) <y.karadz@gmail.com>
>>    */
>>   
>> - /**
>> -  *  @file    libkshark-plot.c
>> -  *  @brief   Basic tools for OpenGL plotting.
>> -  */
>> +/**
>> + *  @file    libkshark-plot.c
>> + *  @brief   Basic tools for OpenGL plotting.
>> + */
>> +
>> +// C
>> +#ifndef _GNU_SOURCE
>> +/** Use GNU C Library. */
>> +#define _GNU_SOURCE
>> +#endif // _GNU_SOURCE
>> +
>> +#include <string.h>
>> +#include <stdio.h>
>>   
>>   // OpenGL
>>   #include <GL/freeglut.h>
>> @@ -16,6 +25,17 @@
>>   // KernelShark
>>   #include "libkshark-plot.h"
>>   
>> +/*
>> + * STB TrueType (single-file public domain library)
>> + * https://github.com/nothings/stb
>> + */
>> +/** Generate implementation. */
>> +#define STB_TRUETYPE_IMPLEMENTATION
>> +
>> +/** Make the implementation private. */
>> +#define STBTT_STATIC
>> +#include "stb_truetype.h"
>> +
>>   /**
>>    * @brief Create an empty scene for drawing.
>>    *
>> @@ -66,7 +86,7 @@ void ksplot_init_opengl(int dpr)
>>   	glEnable(GL_POLYGON_SMOOTH);
>>   	glLineWidth(1.5 * dpr);
>>   	glPointSize(2.5 * dpr);
>> -	glClearColor(1, 1, 1, 1);
>> +	glClearColor(1, 1, 1, 1); // White
>>   }
>>   
>>   /**
>> @@ -210,3 +230,215 @@ void ksplot_draw_polygon_contour(const struct ksplot_point *points,
>>   			 col,
>>   			 size);
>>   }
>> +
>> +/**
>> + * @brief Find a TrueType font file.
>> + *
>> + * @param font_family: The family name of the font.
>> + * @param font_name: The name of the font file without the extention.
>> + *
>> + * @returns A string containing the absolute path to the TrueType font file
>> + *	    on success, or NULL on failure. The user is responsible for freeing
>> + *	    the string.
>> + */
>> +char *ksplot_find_font_file(const char *font_family, const char *font_name)
>> +{
>> +	char buffer[1024], *end;
>> +	char *cmd = NULL;
>> +	int ret;
>> +	FILE *f;
>> +
>> +	ret = asprintf(&cmd, "fc-list \'%s\' |grep %s.ttf", font_family,
>> +							    font_name);
> 
> This is sorta a hack, but for now we can keep it and improve it later, as
> it is wrapped in this function.
> 
> Perhaps add a comment /* FIXME: Do this a bit more properly */

OK, I will add the comment.

> 
> 
>> +	if (ret <= 0)
>> +		goto fail;
>> +
>> +	f = popen(cmd, "r");
>> +	free(cmd);
>> +	if (f == NULL)
>> +		goto fail;
>> +
>> +	end = fgets(buffer, sizeof(buffer), f);
>> +	pclose(f);
>> +	if (!end)
>> +		goto fail;
>> +
>> +	end = strchr(buffer, ':');
>> +	if (!end)
>> +		goto fail;
>> +
>> +	return strndup(buffer, end - buffer);
>> +
>> + fail:
>> +	fprintf(stderr, "Failed to find font file.\n" );
>> +	return NULL;
>> +}
>> +
>> +/** The size of the bitmap matrix used to load the font. */
>> +#define KS_FONT_BITMAP_SIZE 1024
>> +
>> +/**
>> + * @brief Initialize a font.
>> + *
>> + * @param font: Output location for the font descriptor.
>> + * @param size: The size of the font.
>> + * @param file: Input location for the truetype font file.
>> + */
>> +bool ksplot_init_font(struct ksplot_font *font, float size, const char *file)
>> +{
>> +	unsigned char bitmap[KS_FONT_BITMAP_SIZE * KS_FONT_BITMAP_SIZE];
>> +	int ascent, descent, line_gap, lsb;
>> +	ssize_t buff_size, ret;
>> +	unsigned char *buffer;
>> +	stbtt_fontinfo info;
>> +	FILE *font_file;
>> +	float scale;
>> +
>> +	font_file = fopen(file, "rb");
>> +	if (!font_file) {
>> +		fprintf(stderr, "Failed to open font file!\n");
>> +		return false;
>> +	}
>> +
>> +	/* Get the size of the file. */
>> +	fseek(font_file, 0, SEEK_END);
>> +	buff_size = ftell(font_file);
> 
> I would use stat(2) to find the file size.

I will fix this, thanks!

> 
>> +	fseek(font_file, 0, SEEK_SET);
>> +
>> +	buffer = malloc(buff_size);
>> +	if (!buffer) {
>> +		fprintf(stderr, "Failed to allocat memory for font!\n");
>> +		goto close_file;
>> +	}
>> +
>> +	ret = fread(buffer, buff_size, 1, font_file);
>> +	fclose(font_file);
>> +
>> +	if (ret == 0) {
>> +		fprintf(stderr, "Failed to read from font file!\n");
>> +		goto free_buffer;
>> +	}
>> +
>> +	if (!stbtt_InitFont(&info, buffer, 0)) {
>> +		fprintf(stderr, "Failed to init font!\n");
>> +		goto free_buffer;
>> +	}
>> +
>> +	/* Get the font's metrics. */
>> +	scale = stbtt_ScaleForMappingEmToPixels(&info, size);
>> +	stbtt_GetFontVMetrics(&info, &ascent, &descent, &line_gap);
>> +	if (line_gap == 0)
>> +		line_gap = - descent;
>> +	/*
>> +	 * Calculate the dimensions of the font. Note that the descent has
>> +	 * a negative value.
>> +	 */
>> +	font->height = (- descent + ascent + line_gap) * scale;
>> +	font->base = (- descent + line_gap / 2) * scale;
>> +	font->size = size;
>> +
>> +	/*
>> +	 * The width of the 'z' character will be considered as an average
>> +	 * character width.
>> +	 */
>> +	stbtt_GetCodepointHMetrics(&info, 'z', &font->char_width, &lsb);
>> +	font->char_width *= scale;
>> +
>> +	ret = stbtt_BakeFontBitmap(buffer,
>> +				   0,
>> +				   size,
>> +				   bitmap,
>> +				   KS_FONT_BITMAP_SIZE,
>> +				   KS_FONT_BITMAP_SIZE,
>> +				   KS_SPACE_CHAR,
>> +				   KS_N_CHAR,
>> +				   font->cdata);
>> +
>> +	if (ret <= 0) {
>> +		fprintf(stderr, "Failed to bake font bitmap!\n");
>> +		goto free_buffer;
>> +	}
>> +
>> +	free(buffer);
>> +
>> +	glGenTextures(1, &font->texture_id);
>> +	glBindTexture(GL_TEXTURE_2D, font->texture_id);
>> +
>> +	glTexImage2D(GL_TEXTURE_2D,
>> +		     0,
>> +		     GL_ALPHA,
>> +		     KS_FONT_BITMAP_SIZE,
>> +		     KS_FONT_BITMAP_SIZE,
>> +		     0,
>> +		     GL_ALPHA,
>> +		     GL_UNSIGNED_BYTE,
>> +		     bitmap);
>> +
>> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
>> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
>> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
>> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
>> +
> 
> I don't really understand any of the above, so I'm assuming you know what
> it is doing ;-)

;-)

> 
>> +	return true;
>> +
>> + close_file:
>> +	fclose(font_file);
>> +
>> + free_buffer:
>> +	free(buffer);
>> +	return false;
>> +}
>> +
>> +/**
>> + * @brief Print(draw) a text.
>> + *
>> + * @param font: Intput location for the font descriptor.
>> + * @param col: The color of the polygon.
>> + * @param x: Horizontal coordinate of the beginning of the text.
>> + * @param y: Verticalal coordinate of the beginning of the text.
>> + * @param text: The text to be drawn.
>> + */
>> +void ksplot_print_text(const struct ksplot_font *font,
>> +		       const struct ksplot_color *col,
>> +		       float x, float y,
>> +		       const char *text)
>> +{
>> +	glEnable(GL_TEXTURE_2D);
>> +
>> +	/* Set the color of the text. */
>> +	if (col)
>> +		glColor3ub(col->red, col->green, col->blue);
>> +	else
>> +		glColor3ub(0, 0, 0); // Black
>> +
>> +	glBindTexture(GL_TEXTURE_2D, font->texture_id);
>> +	glBegin(GL_QUADS);
>> +	for (; *text; ++text) {
>> +		if (*text < KS_SPACE_CHAR && *text > KS_TILDA_CHAR)
>> +			continue;
>> +
>> +		stbtt_aligned_quad quad;
>> +		stbtt_GetBakedQuad(font->cdata,
>> +				   KS_FONT_BITMAP_SIZE,
>> +				   KS_FONT_BITMAP_SIZE,
>> +				   *text - KS_SPACE_CHAR,
>> +				   &x, &y,
>> +				   &quad,
>> +				   1);
>> +
>> +		glTexCoord2f(quad.s0, quad.t1);
>> +		glVertex2f(quad.x0, quad.y1);
>> +
>> +		glTexCoord2f(quad.s1, quad.t1);
>> +		glVertex2f(quad.x1, quad.y1);
>> +
>> +		glTexCoord2f(quad.s1, quad.t0);
>> +		glVertex2f(quad.x1, quad.y0);
>> +
>> +		glTexCoord2f(quad.s0, quad.t0);
>> +		glVertex2f(quad.x0, quad.y0);
> 
> How is the x and y moved to the next location?

Actually the "y" does not change at all here, because for the moment we 
can't draw multi-line text. "x" gets incremented inside 
stbtt_GetBakedQuad(). The horizontal advance of the character is used to 
calculate the new position.

Thanks a lot!
Yordan

> 
>> +	}
>> +
>> +	glEnd();
>> +	glDisable(GL_TEXTURE_2D);
>> +}
>> diff --git a/src/libkshark-plot.h b/src/libkshark-plot.h
>> index 9a4dbc02..0edf5d50 100644
>> --- a/src/libkshark-plot.h
>> +++ b/src/libkshark-plot.h
>> @@ -12,6 +12,15 @@
>>   #ifndef _LIB_KSHARK_PLOT_H
>>   #define _LIB_KSHARK_PLOT_H
>>   
>> +// C
>> +#include <stdbool.h>
>> +
>> +/*
>> + * STB TrueType (single-file public domain library)
>> + * https://github.com/nothings/stb
>> + */
>> +#include "stb_truetype.h"
>> +
>>   #ifdef __cplusplus
>>   extern "C" {
>>   #endif
>> @@ -62,6 +71,54 @@ void ksplot_draw_polygon_contour(const struct ksplot_point *points,
>>   				 const struct ksplot_color *col,
>>   				 float size);
>>   
>> +/** The index of the "Space" character. */
>> +#define KS_SPACE_CHAR 32
>> +
>> +/** The index of the "Tilda" character. */
>> +#define KS_TILDA_CHAR 126
>> +
>> +/** Total number of characters supported for drawing. */
>> +#define KS_N_CHAR (KS_TILDA_CHAR - KS_SPACE_CHAR + 1)
>> +
>> +/** Structure defining a font. */
>> +struct ksplot_font {
>> +	/** Identifier of the font's texture. */
>> +	GLuint texture_id;
>> +
>> +	/** Font's texture baking data. */
>> +	stbtt_bakedchar cdata[KS_N_CHAR];
>> +
>> +	/** The height of a text line. */
>> +	int height;
>> +
>> +	/** The vertical position of the font's baseline. */
>> +	int base;
>> +
>> +	/** The size of the font. */
>> +	int size;
>> +
>> +	/**
>> +	 * The width of the 'z' character. To be use as an average character
>> +	 * width.
>> +	 */
>> +	int char_width;
>> +};
>> +
>> +/** Check if the texture of the font is loaded. */
>> +static inline bool ksplot_font_is_loaded(struct ksplot_font *f)
>> +{
>> +	return f->texture_id > 1;
>> +}
>> +
>> +char *ksplot_find_font_file(const char *font_family, const char *font_name);
>> +
>> +bool ksplot_init_font(struct ksplot_font *font, float size, const char *file);
>> +
>> +void ksplot_print_text(const struct ksplot_font *font,
>> +		       const struct ksplot_color *col,
>> +		       float x, float y,
>> +		       const char *text);
>> +
>>   #ifdef __cplusplus
>>   }
>>   #endif
>> diff --git a/src/stb_truetype.h b/src/stb_truetype.h
>> new file mode 100644
>> index 00000000..62595a15
>> --- /dev/null
>> +++ b/src/stb_truetype.h
> 
> I'm assuming the rest is what you took from public domain?
> 
>> @@ -0,0 +1,5011 @@
>> +// stb_truetype.h - v1.24 - public domain
>> +// authored from 2009-2020 by Sean Barrett / RAD Game Tools
>> +//
>> +// =======================================================================
>> +//
>> +//    NO SECURITY GUARANTEE -- DO NOT USE THIS ON UNTRUSTED FONT FILES
>> +//
>> +// This library does no range checking of the offsets found in the file,
>> +// meaning an attacker can use it to read arbitrary memory.
>> +//
>> +// =======================================================================
>> +//
>> +//   This library processes TrueType files:
>> +//        parse files
>> +//        extract glyph metrics
>> +//        extract glyph shapes
>> +//        render glyphs to one-channel bitmaps with antialiasing (box filter)
>> +//        render glyphs to one-channel SDF bitmaps (signed-distance field/function)
>> +//
>> +//   Todo:
>> +//        non-MS cmaps
>> +//        crashproof on bad data
>> +//        hinting? (no longer patented)
>> +//        cleartype-style AA?
>> +//        optimize: use simple memory allocator for intermediates
>> +//        optimize: build edge-list directly from curves
>> +//        optimize: rasterize directly from curves?
>> +//
>> +// ADDITIONAL CONTRIBUTORS
>> +//
>> +//   Mikko Mononen: compound shape support, more cmap formats
>> +//   Tor Andersson: kerning, subpixel rendering
>> +//   Dougall Johnson: OpenType / Type 2 font handling
>> +//   Daniel Ribeiro Maciel: basic GPOS-based kerning
> 
> [..]
>