Dear all,
I'm working on CLIM-PDF backend and I solved some problems like the text direction in landscape orientation, but I don't like the solution so I didn't submit any PR.
Instead I write here to have some feedback from you about some issues that I have found, some very PDF specific other in the very core of McCLIM.
I'm start from the more pdf specific (and easier) to the more general one (and harder):
1) WITH-OUTPUT-TO-PDF-STREAM macro:
The PDF backend is used through WITH-OUTPUT-TO-PDF-STREAM that is based on the analogous macro for Postscript backend defined in the Spec.
I think it is better to define for PDF backend a WITH-OUTPUT-TO-PDF-FILE with a string or a pathname as argument instead of a stream. In this way the user don't have to open the file stream (the user needs also to known that the stream must be open with keyword :element-type '(unsigned-byte 8)). If we remove the WITH-OUTPUT-TO-PDF-STREAM McCLIM can remove the dependency to FLEXI-STREM system.
The difference from PDF to Postscript is giustified because PDF is a file format so the output is ever a file, instead the Postscript output can be send on a stream directly atttached to a postscript printer.
We can also add a WITH-OUTPUT-TO-POSTSCRIPT-FILE macro without remove the WITH-OUTPUT-TO-POSTSCRIPT-STREAM defined in the Specification.
2) GRAFT in PDF and Postscript Backend
PDF and Postscript Backend define their GRAFT but then never use it. The stream sheet where the output is drawn is not a child of a graft. I think this is not correct.
3) GRAFT in general
Now each backend define its GRAFT. I think that the backend could only initialize a standard-graft with the right information (in MAKE-GRAFT generic) like: mirror, width, height, device-millimiter-density, backend-transformation, and leave all the other stuff in the common graft module "Core/clim-basic/windowing/grafts.lisp"
4) transformation and region machinery
Is it the transformation and region machinery correct? Or it is works only in some standard situaions? For example I think that we could obtain a Zoom effect simply by: (setf (sheet-transformation some-sheet) (make-scaling-transformation 1.5 1.5)) but this doesn't work on McCLIM (I try it in the listener demo of clim-tos and there it works). Follow some more specific topics:
4a) Setting sheet-native-transformation:
McCLIM set directly the SHEET-NATIVE-TRANSFORMATION with %%SET-SHEET-NATIVE-TRANSFORMATION. I think this is not correct the sheet-native-transformation must be computated and only cached never set directly, otherwise you can lost the parent trasformation.
4b) sheet-native-transformation for basic-sheet:
(defmethod sheet-native-transformation ((sheet basic-sheet)) (with-slots (native-transformation) sheet (unless native-transformation (setf native-transformation (if-let ((parent (sheet-parent sheet))) (compose-transformations (sheet-native-transformation parent) (sheet-transformation sheet)) +identity-transformation+))) native-transformation))
it's not correct because didn't take in account the mirror transformation if the mirror of sheet it is not the same of the parent. So we need to correct this or to add a method for mirrored-sheet-mixin. Of course we didn't see the error because often McCLIM set directly sheet-native-transform as written before in 4a)
4c) What is sheet-native-region?
From the spec: "Returns the region for the sheet sheet in native
coordinates". This is not clear. The first time that I read it I understood that it is the sheet-region of the sheet transformed in native coordinates, that means for examples that a sheet with a region +everywhere+ have a native-region +everywhere+. Instead for McCLIM, and clim-tos too, it is the region of the mirror "for" the sheet i.e. the sheet-region of the sheet transformed in native coordinates clipped by the mirror region. This interpretation maybe is correct because the spec said about sheet-device-region:
"Returns the actual clipping region to be used when drawing on the mirror. This is the intersection of the user's clipping region (transformed by the device transformation) with the sheet's native region."
Anyway, in this case, the sheet-native-region for the graft in Mcclim is wrong: it is +everywhere+