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 <cstdlib>
#include <cstring>
#include <memory>
 
#include "gvplugin_gdiplus.h"
#include <gvc/gvplugin_textlayout.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);
  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(),
                                  static_cast<REAL>(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}};