gvtextlayout_gdiplus.cpp

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#include "config.h"
 
#include <memory>
#include <stdlib.h>
#include <string.h>
 
#include <gvc/gvplugin_textlayout.h>
#include "gvplugin_gdiplus.h"
 
using namespace Gdiplus;
 
static int CALLBACK fetch_first_font(const LOGFONTA *logFont,
                                     const TEXTMETRICA *, DWORD, LPARAM lParam)
{
        /* save the first font we see in the font enumeration */
        *((LOGFONTA *)lParam) = *logFont;
        return 0;
}
 
Layout::Layout(char *fontname, double fontsize, char* string)
{
        /* convert incoming UTF8 string to wide chars */
        /* NOTE: conversion is 1 or more UTF8 chars to 1 wide char */
        int len = strlen(string);
        text.resize(len);
        text.resize(MultiByteToWideChar(CP_UTF8, 0, string, len, &text[0], len));
 
        /* search for a font with this name. if we can't find it, use the generic serif instead */
        /* NOTE: GDI font search is more comprehensive than GDI+ and will look for variants e.g. Arial Bold */
        DeviceContext reference;
        LOGFONTA font_to_find;
        font_to_find.lfCharSet = ANSI_CHARSET;
        size_t font_len = strlen(fontname);
        if (font_len > sizeof(font_to_find.lfFaceName) - 1) {
                font_len = sizeof(font_to_find.lfFaceName) - 1;
        }
        memcpy(font_to_find.lfFaceName, fontname, font_len);
        font_to_find.lfFaceName[sizeof(font_to_find.lfFaceName) - 1] = '\0';
        font_to_find.lfPitchAndFamily = 0;
        LOGFONTA found_font;
        if (EnumFontFamiliesExA(reference.hdc,
                &font_to_find,
                fetch_first_font,
                (LPARAM)&found_font,
                0) == 0) {
                found_font.lfHeight = (LONG)-fontsize;
                found_font.lfWidth = 0;
                font = std::make_unique<Font>(reference.hdc, &found_font);
        }
        else
                font = std::make_unique<Font>(FontFamily::GenericSerif(), fontsize);
}
 
void gdiplus_free_layout(void *layout)
{
        if (layout)
                delete reinterpret_cast<Layout*>(layout);
};
 
bool gdiplus_textlayout(textspan_t *span, char **)
{
        /* ensure GDI+ is started up: since we get called outside of a job, we can't rely on GDI+ startup then */
        UseGdiplus();
 
        Layout* layout = new Layout(span->font->name, span->font->size, span->str);
 
        /* measure the text */
        /* NOTE: use TextRenderingHintAntiAlias + GetGenericTypographic to get a layout without extra space at beginning and end */
        RectF boundingBox;
        DeviceContext deviceContext;
        Graphics measureGraphics(deviceContext.hdc);
        measureGraphics.SetTextRenderingHint(TextRenderingHintAntiAlias);
        measureGraphics.MeasureString(
                &layout->text[0],
                layout->text.size(),
                layout->font.get(),
                PointF(0.0f, 0.0f),
                GetGenericTypographic(),
                &boundingBox);
 
        FontFamily fontFamily;
        layout->font->GetFamily(&fontFamily);
        int style = layout->font->GetStyle();
 
        span->layout = layout;
        span->free_layout = &gdiplus_free_layout;
        span->size.x = boundingBox.Width;
        span->size.y = layout->font->GetHeight(&measureGraphics);
        span->yoffset_layout = fontFamily.GetCellAscent(style) * span->font->size / fontFamily.GetEmHeight(style); /* convert design units to pixels */
        span->yoffset_centerline = 0;
        return true;
};
 
static gvtextlayout_engine_t gdiplus_textlayout_engine = {
    gdiplus_textlayout
};
 
gvplugin_installed_t gvtextlayout_gdiplus_types[] = {
    {0, "textlayout", 8, &gdiplus_textlayout_engine, nullptr},
    {0, nullptr, 0, nullptr, nullptr}
};