149 lines
4.1 KiB
C++
149 lines
4.1 KiB
C++
/*
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* \brief Functor for drawing glyphs
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* \author Norman Feske
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* \date 2006-08-04
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*/
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/*
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* Copyright (C) 2006-2018 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__NITPICKER_GFX__GLYPH_PAINTER_H_
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#define _INCLUDE__NITPICKER_GFX__GLYPH_PAINTER_H_
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#include <util/noncopyable.h>
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#include <base/stdint.h>
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#include <os/surface.h>
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struct Glyph_painter
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{
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/**
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* Subpixel positions are represented as fixpoint numbers that use 24 bits
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* for the decimal and 8 bits for the fractional part.
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*/
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struct Fixpoint_number
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{
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int value;
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Fixpoint_number(float value) : value(value*256) { };
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Fixpoint_number(int decimal) : value(decimal << 8) { };
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int decimal() const { return value >> 8; }
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};
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typedef Genode::Point<Fixpoint_number> Position;
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struct Glyph
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{
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unsigned const width;
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unsigned const height;
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unsigned const vpos;
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Fixpoint_number const advance;
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struct Opacity { unsigned char value; };
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/**
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* Pointer to opacity values (0 = transparent, 255 = opaque)
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*
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* The 'values' buffer contains the glyph horizontally scaled by four.
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* Its size is width*4*height bytes. The first row (four values) of each
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* line as well as the last line contains padding space, which does not
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* need to be drawn in order to obtain the complete shape.
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*/
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Opacity const * const values;
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unsigned num_values() const { return 4*width*height; }
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};
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/**
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* Draw single glyph on a 'dst' buffer, with clipping applied
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*
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* In contrast to most painter functions, which operate on a 'Surface',
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* this function has a lower-level interface. It is intended as a utility
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* called by painter implementations, not by applications directly.
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*/
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template <typename PT>
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static inline void paint(Position const position, Glyph const &glyph,
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PT *dst, unsigned const dst_line_len,
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int const clip_top, int const clip_bottom,
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int const clip_left, int const clip_right,
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PT const color, int const alpha)
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{
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Fixpoint_number const x = position.x();
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int const y = position.y().decimal();
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int const dst_y1 = y + glyph.vpos,
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dst_y2 = dst_y1 + glyph.height;
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unsigned const clipped_from_top = clip_top > dst_y1
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? clip_top - dst_y1 : 0;
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unsigned const clipped_from_bottom = dst_y2 > clip_bottom
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? dst_y2 - clip_bottom : 0;
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if (clipped_from_top + clipped_from_bottom >= glyph.height)
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return;
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unsigned const num_lines = glyph.height - clipped_from_top
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- clipped_from_bottom;
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int const w = glyph.width;
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int const start = Genode::max(0, clip_left - x.decimal());
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int const end = Genode::min(w - 1, clip_right - x.decimal());
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int const dst_x = start + ((x.value) >> 8);
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int const glyph_x = start*4 + 3 - ((x.value & 0xc0) >> 6);
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unsigned const glyph_line_len = 4*glyph.width;
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PT *dst_column = dst + dst_x
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+ dst_line_len*(dst_y1 + clipped_from_top);
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typedef Glyph::Opacity Opacity;
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Opacity const *glyph_column = glyph.values + glyph_x
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+ glyph_line_len*clipped_from_top;
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/* iterate over the visible columns of the glyph */
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for (int i = start; i < end; i++) {
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/* weights of the two sampled values (horizontal neighbors)*/
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int const u0 = x.value*4 & 0xff;
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int const u1 = 0x100 - u0;
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PT *d = dst_column;
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Opacity const *s = glyph_column;
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/* iterate over one column */
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for (unsigned j = 0; j < num_lines; j++) {
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/* sample values from glyph image */
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unsigned const v0 = s->value;
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unsigned const v1 = (s + 1)->value;
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/* apply weights */
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int const value = (v0*u0 + v1*u1) >> 8;
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/* transfer pixel */
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if (value)
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*d = (value == 255 && alpha == 255)
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? color : PT::mix(*d, color, (alpha*value) >> 8);
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s += glyph_line_len;
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d += dst_line_len;
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}
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dst_column += 1;
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glyph_column += 4;
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}
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}
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};
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#endif /* _INCLUDE__NITPICKER_GFX__GLYPH_PAINTER_H_ */
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