| /* |
| * Copyright 2020 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/gpu/text/GrSDFTOptions.h" |
| |
| #include "include/core/SkFont.h" |
| #include "include/core/SkMatrix.h" |
| #include "include/core/SkPaint.h" |
| #include "include/core/SkScalar.h" |
| #include "include/core/SkSurfaceProps.h" |
| |
| #include <tuple> |
| |
| // DF sizes and thresholds for usage of the small and medium sizes. For example, above |
| // kSmallDFFontLimit we will use the medium size. The large size is used up until the size at |
| // which we switch over to drawing as paths as controlled by Options. |
| static const int kSmallDFFontSize = 32; |
| static const int kSmallDFFontLimit = 32; |
| static const int kMediumDFFontSize = 72; |
| static const int kMediumDFFontLimit = 72; |
| static const int kLargeDFFontSize = 162; |
| #ifdef SK_BUILD_FOR_MAC |
| static const int kLargeDFFontLimit = 162; |
| static const int kExtraLargeDFFontSize = 256; |
| #endif |
| |
| GrSDFTOptions::GrSDFTOptions(SkScalar min, SkScalar max) |
| : fMinDistanceFieldFontSize{min} |
| , fMaxDistanceFieldFontSize{max} { |
| SkASSERT_RELEASE(min > 0 && max >= min); |
| } |
| |
| bool GrSDFTOptions::canDrawAsDistanceFields(const SkPaint& paint, const SkFont& font, |
| const SkMatrix& viewMatrix, |
| const SkSurfaceProps& props, |
| bool contextSupportsDistanceFieldText) const { |
| // mask filters modify alpha, which doesn't translate well to distance |
| if (paint.getMaskFilter() || !contextSupportsDistanceFieldText) { |
| return false; |
| } |
| |
| // TODO: add some stroking support |
| if (paint.getStyle() != SkPaint::kFill_Style) { |
| return false; |
| } |
| |
| if (viewMatrix.hasPerspective()) { |
| // Don't use SDF for perspective. Paths look better. |
| return false; |
| } else { |
| SkScalar maxScale = viewMatrix.getMaxScale(); |
| SkScalar scaledTextSize = maxScale * font.getSize(); |
| // Hinted text looks far better at small resolutions |
| // Scaling up beyond 2x yields undesirable artifacts |
| if (scaledTextSize < fMinDistanceFieldFontSize || |
| scaledTextSize > fMaxDistanceFieldFontSize) { |
| return false; |
| } |
| |
| bool useDFT = props.isUseDeviceIndependentFonts(); |
| #if SK_FORCE_DISTANCE_FIELD_TEXT |
| useDFT = true; |
| #endif |
| |
| if (!useDFT && scaledTextSize < kLargeDFFontSize) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| SkScalar scaled_text_size(const SkScalar textSize, const SkMatrix& viewMatrix) { |
| SkScalar scaledTextSize = textSize; |
| |
| if (viewMatrix.hasPerspective()) { |
| // for perspective, we simply force to the medium size |
| // TODO: compute a size based on approximate screen area |
| scaledTextSize = kMediumDFFontLimit; |
| } else { |
| SkScalar maxScale = viewMatrix.getMaxScale(); |
| // if we have non-unity scale, we need to choose our base text size |
| // based on the SkPaint's text size multiplied by the max scale factor |
| // TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)? |
| if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) { |
| scaledTextSize *= maxScale; |
| } |
| } |
| |
| return scaledTextSize; |
| } |
| |
| SkFont GrSDFTOptions::getSDFFont(const SkFont& font, |
| const SkMatrix& viewMatrix, |
| SkScalar* textRatio) const { |
| SkScalar textSize = font.getSize(); |
| SkScalar scaledTextSize = scaled_text_size(textSize, viewMatrix); |
| |
| SkFont dfFont{font}; |
| |
| if (scaledTextSize <= kSmallDFFontLimit) { |
| *textRatio = textSize / kSmallDFFontSize; |
| dfFont.setSize(SkIntToScalar(kSmallDFFontSize)); |
| } else if (scaledTextSize <= kMediumDFFontLimit) { |
| *textRatio = textSize / kMediumDFFontSize; |
| dfFont.setSize(SkIntToScalar(kMediumDFFontSize)); |
| #ifdef SK_BUILD_FOR_MAC |
| } else if (scaledTextSize <= kLargeDFFontLimit) { |
| *textRatio = textSize / kLargeDFFontSize; |
| dfFont.setSize(SkIntToScalar(kLargeDFFontSize)); |
| } else { |
| *textRatio = textSize / kExtraLargeDFFontSize; |
| dfFont.setSize(SkIntToScalar(kExtraLargeDFFontSize)); |
| } |
| #else |
| } else { |
| *textRatio = textSize / kLargeDFFontSize; |
| dfFont.setSize(SkIntToScalar(kLargeDFFontSize)); |
| } |
| #endif |
| |
| dfFont.setEdging(SkFont::Edging::kAntiAlias); |
| dfFont.setForceAutoHinting(false); |
| dfFont.setHinting(SkFontHinting::kNormal); |
| |
| // The sub-pixel position will always happen when transforming to the screen. |
| dfFont.setSubpixel(false); |
| return dfFont; |
| } |
| |
| std::pair<SkScalar, SkScalar> GrSDFTOptions::computeSDFMinMaxScale( |
| SkScalar textSize, const SkMatrix& viewMatrix) const { |
| |
| SkScalar scaledTextSize = scaled_text_size(textSize, viewMatrix); |
| |
| // We have three sizes of distance field text, and within each size 'bucket' there is a floor |
| // and ceiling. A scale outside of this range would require regenerating the distance fields |
| SkScalar dfMaskScaleFloor; |
| SkScalar dfMaskScaleCeil; |
| if (scaledTextSize <= kSmallDFFontLimit) { |
| dfMaskScaleFloor = fMinDistanceFieldFontSize; |
| dfMaskScaleCeil = kSmallDFFontLimit; |
| } else if (scaledTextSize <= kMediumDFFontLimit) { |
| dfMaskScaleFloor = kSmallDFFontLimit; |
| dfMaskScaleCeil = kMediumDFFontLimit; |
| } else { |
| dfMaskScaleFloor = kMediumDFFontLimit; |
| dfMaskScaleCeil = fMaxDistanceFieldFontSize; |
| } |
| |
| // Because there can be multiple runs in the blob, we want the overall maxMinScale, and |
| // minMaxScale to make regeneration decisions. Specifically, we want the maximum minimum scale |
| // we can tolerate before we'd drop to a lower mip size, and the minimum maximum scale we can |
| // tolerate before we'd have to move to a large mip size. When we actually test these values |
| // we look at the delta in scale between the new viewmatrix and the old viewmatrix, and test |
| // against these values to decide if we can reuse or not(ie, will a given scale change our mip |
| // level) |
| SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil); |
| |
| return std::make_pair(dfMaskScaleFloor / scaledTextSize, dfMaskScaleCeil / scaledTextSize); |
| } |
| |
| |