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Shorten Agg template usage with class template argument deduction.
Many parts of the Agg & path processing pipeline work by constructing nested templated objects that represent steps of the processing pipeline, e.g. (simplified example) ``` agg::conv_transform<mpl::PathIterator> // The processing step. tpath // The name of the result. (path, trans); // The arguments passed to the processing step. PathNanRemover<agg::conv_transform<mpl::PathIterator>> nan_removed (tpath, true, path.has_codes()); ``` The current implementation makes the code shorter by introducing alias typenames for the types at each intermediate step. As of C++17, this can be made simpler and shorter because class template argument deduction ("CTAD") allows not specifying the template arguments (in angle brackets) anymore, i.e. one can write ``` agg::conv_transform tpath(path, trans); PathNanRemover nan_removed(tpath, true, path.has_codes()); ``` and the compiler will auto-fill in the required types. Furthermore, because these steps can be seen as a pipeline (even though they are implemented as the construction of nested objects), it may feel more natural to write them as repeated "function" (constructor) application, i.e. ``` auto tpath = agg::conv_transform{path, trans}; auto nan_removed = PathNanRemover{tpath, true, path.has_codes()}; ``` Perform this transformation whereever applicable.
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‎src/_backend_agg.cpp

Lines changed: 13 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -122,15 +122,6 @@ bool RendererAgg::render_clippath(mpl::PathIterator &clippath,
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const agg::trans_affine &clippath_trans,
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e_snap_mode snap_mode)
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{
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typedef agg::conv_transform<mpl::PathIterator> transformed_path_t;
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typedef PathNanRemover<transformed_path_t> nan_removed_t;
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/* Unlike normal Paths, the clip path cannot be clipped to the Figure bbox,
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* because it needs to remain a complete closed path, so there is no
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* PathClipper<nan_removed_t> step. */
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typedef PathSnapper<nan_removed_t> snapped_t;
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typedef PathSimplifier<snapped_t> simplify_t;
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typedef agg::conv_curve<simplify_t> curve_t;
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bool has_clippath = (clippath.total_vertices() != 0);
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if (has_clippath &&
@@ -141,13 +132,19 @@ bool RendererAgg::render_clippath(mpl::PathIterator &clippath,
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trans *= agg::trans_affine_translation(0.0, (double)height);
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rendererBaseAlphaMask.clear(agg::gray8(0, 0));
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transformed_path_t transformed_clippath(clippath, trans);
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nan_removed_t nan_removed_clippath(transformed_clippath, true, clippath.has_codes());
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snapped_t snapped_clippath(nan_removed_clippath, snap_mode, clippath.total_vertices(), 0.0);
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simplify_t simplified_clippath(snapped_clippath,
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clippath.should_simplify() && !clippath.has_codes(),
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clippath.simplify_threshold());
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curve_t curved_clippath(simplified_clippath);
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auto transformed_clippath = agg::conv_transform{clippath, trans};
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auto nan_removed_clippath = PathNanRemover{
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transformed_clippath, true, clippath.has_codes()};
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// Unlike normal Paths, the clip path cannot be clipped to the Figure
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// bbox, because it needs to remain a complete closed path, so there is
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// no PathClipper step after nan-removal.
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auto snapped_clippath = PathSnapper{
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nan_removed_clippath, snap_mode, clippath.total_vertices(), 0.0};
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auto simplified_clippath = PathSimplifier{
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snapped_clippath,
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clippath.should_simplify() && !clippath.has_codes(),
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clippath.simplify_threshold()};
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auto curved_clippath = agg::conv_curve{simplified_clippath};
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theRasterizer.add_path(curved_clippath);
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rendererAlphaMask.color(agg::gray8(255, 255));
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agg::render_scanlines(theRasterizer, scanlineAlphaMask, rendererAlphaMask);

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