office-gobmx/include/drawinglayer/primitive2d/textlayoutdevice.hxx
Mike Kaganski cc3663bbae tdf#160702: improve text positioning
Opening an SVG with text in different elements (e.g., tspans) in the
same text element performs calculations to position the parts properly
(i.e., the next part will start where the previous part ended, unless
the position in overridden explicitly). These calculations require to
know the text widths. The first problem leas here: the text width was
calculated for a typically small text size (numerically equal to the
pixel size defined in the SVG), but these calculations aren't truly
linear, because font rendering may change depending on font height.
Additionally, the rounding gives much higher error in smaller sizes
than in larger. There was already a workaround for a similar problem
in ViewRedirector::createRedirectedPrimitive2DSequence, where a large
font (with 100 times greater height) was used to increase correctness.
This was also used here, with the same large height (50000) used as a
reference.

Then, at the time of wrawing the text at different zoom levels, the
code in VclProcessor2D::RenderTextSimpleOrDecoratedPortionPrimitive2D
creates a font of a calculated size, and uses it to output the text.
But the font is always created with an integral height, which means,
that for a wanted height of 2.5 (in a zoomed out view), the really
used height will be 3, which is 20% larger; or for wanted height of
2.4, the actual height will be 2 (20% smaller). This resulted in odd
jumps of the text widths, when the text may overlap the following
part, or conversely, create a big gap before the next gap. To try to
mitigate that, the function now takes the difference between the
wanted and the actual font size into account, and adjusts the MapMode
accordingly. This doesn't fix the jumping completely (e.g., because
of the mentioned special handling of small font sizes in the fonts
thenselves, like hinting), but still makes the calculations much more
stable, decreasing the amount of jumping. Similar changes are made in
TextLayouterDevice.

Use of the functions that return text size as a double, not rounded
value, should additionally help improving stability.

Change-Id: I455845d8ca43ee9c06a0fc980947f35d8a25797a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/166238
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
2024-04-20 11:28:34 +02:00

127 lines
4.5 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#pragma once
#include <drawinglayer/drawinglayerdllapi.h>
#include <basegfx/range/b2drange.hxx>
#include <vector>
#include <basegfx/polygon/b2dpolypolygon.hxx>
#include <vcl/svapp.hxx>
// predefines
class VirtualDevice;
class GDIMetaFile;
enum class DrawTextFlags;
namespace vcl
{
class Font;
}
namespace tools
{
class Rectangle;
}
namespace drawinglayer::attribute
{
class FontAttribute;
}
namespace com::sun::star::lang
{
struct Locale;
}
// access to one global impTimedRefDev incarnation in namespace drawinglayer::primitive
namespace drawinglayer::primitive2d
{
/** TextLayouterDevice class
This helper class exists to isolate all accesses to VCL
text formatting/handling functionality for primitive implementations.
When in the future FontHandling may move to an own library independent
from VCL, primitives will be prepared.
*/
class DRAWINGLAYER_DLLPUBLIC TextLayouterDevice
{
/// internally used VirtualDevice
SolarMutexGuard maSolarGuard;
VirtualDevice& mrDevice;
double mnFontScalingFixX = 1.0;
double mnFontScalingFixY = 1.0;
public:
/// constructor/destructor
TextLayouterDevice();
~TextLayouterDevice() COVERITY_NOEXCEPT_FALSE;
/// tooling methods
void setFont(const vcl::Font& rFont);
void setFontAttribute(const attribute::FontAttribute& rFontAttribute, double fFontScaleX,
double fFontScaleY, const css::lang::Locale& rLocale);
double getTextHeight() const;
double getOverlineHeight() const;
double getOverlineOffset() const;
double getUnderlineHeight() const;
double getUnderlineOffset() const;
double getStrikeoutOffset() const;
double getTextWidth(const OUString& rText, sal_uInt32 nIndex, sal_uInt32 nLength) const;
void getTextOutlines(basegfx::B2DPolyPolygonVector&, const OUString& rText, sal_uInt32 nIndex,
sal_uInt32 nLength, const ::std::vector<double>& rDXArray,
const ::std::vector<sal_Bool>& rKashidaArray) const;
basegfx::B2DRange getTextBoundRect(const OUString& rText, sal_uInt32 nIndex,
sal_uInt32 nLength) const;
double getFontAscent() const;
double getFontDescent() const;
void addTextRectActions(const tools::Rectangle& rRectangle, const OUString& rText,
DrawTextFlags nStyle, GDIMetaFile& rGDIMetaFile) const;
::std::vector<double> getTextArray(const OUString& rText, sal_uInt32 nIndex, sal_uInt32 nLength,
bool bCaret = false) const;
};
// helper methods for vcl font handling
/** Create a VCL-Font based on the definitions in FontAttribute
and the given FontScaling. The FontScaling defines the FontHeight
(fFontScaleY) and the FontWidth (fFontScaleX). The combination of
both defines FontStretching, where no stretching happens at
fFontScaleY == fFontScaleX
*/
vcl::Font DRAWINGLAYER_DLLPUBLIC getVclFontFromFontAttribute(
const attribute::FontAttribute& rFontAttribute, double fFontScaleX, double fFontScaleY,
double fFontRotation, const css::lang::Locale& rLocale);
/** Generate FontAttribute DataSet derived from the given VCL-Font.
The FontScaling with fFontScaleY, fFontScaleX relationship (see
above) will be set in return parameter o_rSize to allow further
processing
*/
attribute::FontAttribute DRAWINGLAYER_DLLPUBLIC getFontAttributeFromVclFont(
basegfx::B2DVector& o_rSize, const vcl::Font& rFont, bool bRTL, bool bBiDiStrong);
} // end of namespace drawinglayer::primitive2d
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */