Hello zyx, PoDoFo devs,
an update on the PdfPainter situation: a rework of the PdfPainter has
been carried out to address some reviews/concerns. It follows the
changes and design notes:
- The previously described path "context" has been renamed/moved to a
PdfPainterPath[1] class, now representing an external path in
construction. The class allows to retrieve a string view of the path
currently being built, and can be drawn/clipped with
PdfPainter::DrawPath/ClipPath;
- A base "interface" like PdfContentStreamOperators[2] class has been
introduced offering a low level content stream manipulation layer to
be used by power users. PdfPainter implements all the methods of the
class privately: such low level functionalities can be retrieved by
casting the painter instance to PdfContentStreamOperators. It is worth
to add that such functionalities are still partially validated by the
internal state of the painter;
- PdfPainter and PdfPainterPath still offer an easy to use high level
interface for Pdf drawing operations, and now even more closely match
the API design of .NET Graphics and GraphicsPath class (to zyx for
reference: NET Graphics is really a MS official wrapper around HDC/GDI
Windows API);
- The text "context" has been renamed to PdfPainterTextObject, and the
PdfPainter::Text instance renamed to TextObject, to reflect the PDF
specification naming. This remains an interface to manually handle BT
.. ET stacking and add continuous text. The high level text API to draw
text remains PdfPainter::DrawText like functions.
I also privately received some feedback that relates to writing proper
glyph positioning: a status describing the painter being constructing
glyphs array ("[ gliphs1 delta glyps2 ... ] TJ") and glyph arrays writing
primitives were added. These should help in the future to the
introduction of text shaping with HarfBuzz[3].
It follows an example of use of the updated API:
PdfPainter painter;
painter.SetCanvas(page);
painter.TextState.SetFont(font, 15);
painter.DrawText("Test2", 100, 600, PdfDrawTextStyle::StrikeOut);
painter.TextObject.Begin();
painter.TextObject.MoveTo(100, 500);
painter.TextObject.AddText("Test");
painter.TextObject.End();
painter.GraphicsState.SetLineWidth(1);
PdfPainterPath path;
path.MoveTo(20, 20);
path.AddArcTo(150, 20, 150, 70, 50);
path.AddLineTo(150, 120);
painter.DrawPath(path, PdfPathDrawMode::Stroke);
path.Reset();
path.MoveTo(40, 40);
path.AddLineTo(100, 40);
path.AddLineTo(70, 80);
path.AddLineTo(40, 40);
path.AddCircle(200, 200, 60);
painter.DrawPath(path, PdfPathDrawMode::Fill);
painter.Save();
const double SquareSize = 6;
painter.GraphicsState.SetLineWidth(0.6);
painter.DrawRectangle(150 - SquareSize / 2, 70 - SquareSize / 2,
SquareSize, SquareSize);
painter.GraphicsState.SetLineWidth(0);
painter.DrawLine(150, 70 - SquareSize / 2, 150, 70 + SquareSize / 2);
painter.DrawLine(150 - SquareSize / 2, 70, 150 + SquareSize / 2, 70);
painter.Restore();
Here it follows an example of use of the low level interface:
auto& operators = static_cast<PdfContentStreamOperators&>(painter);
painter.TextObject.Begin();
painter.TextObject.MoveTo(100, 500);
// Some low level operations
operators.TJ_Operator_Begin();
operators.TJ_Operator_Glyphs("W", false);
operators.TJ_Operator_Delta(-500);
operators.TJ_Operator_Glyphs("orld", false);
operators.TJ_Operator_End();
painter.TextObject.End();
The goal of the PdfPainter revamp isn't being a 100% complete drawing
API, but put a more robust foundation for growing in the future
releases. If you have any further comment/review (can be as simple as
suggesting better names for classes/members), please don't be shy to
reply publicly: this makes the development process more transparent
and motivates me in replying. As soon as there are no concerns that
require immediate modifications, we can freeze the API and complete
few more bugfixes heading for a 0.10 release.
Cheers,
Francesco
[1]
https://github.com/podofo/podofo/blob/master/src/podofo/main/PdfPainterPath.h
[2]
https://github.com/podofo/podofo/blob/master/src/podofo/main/PdfContentStreamOperators.h
[3] https://github.com/harfbuzz/harfbuzz
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