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win32: adjust printing-dc% scale to simulate screen DPI

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This is questionable; it might be better to set up a printing
 context with 72 DPI and adjust the resolution of the Pango
 font map associated with the DC to be 72 DPI; matching the
 screen is easier, and it provides the benefit that font metrics
 (based on fonts with point sizes rather than pixel sizes) are
 consistent across drawing contexts

original commit: 0d36dbefb8a5fed1d1b69cabdd1aa039566553c9
This commit is contained in:
Matthew Flatt 2011-01-13 20:05:34 -07:00
parent bdc443ab33
commit 4a5dc5b76b
1 changed files with 17 additions and 9 deletions
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26
collects/mred/private/wx/win32/printer-dc.rkt
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@ -78,6 +78,11 @@
(define-gdi32 EndPage (_wfun _HDC -> (r : _int) -> (unless (positive? r) (failed 'EndPage))))
(define-gdi32 EndDoc (_wfun _HDC -> (r : _int) -> (unless (positive? r) (failed 'EndDoc))))
(define-gdi32 GetDeviceCaps (_wfun _HDC _int -> _int))
(define LOGPIXELSX 88)
(define LOGPIXELSY 90)
(define needs-delete ((allocator DeleteDC) values))
(define (clone-page-setup p)
@ -111,6 +116,14 @@
;; the hDevModes and hDevNames fields
r)))))
;; Pango uses the resolution of the screen to make point<->pixel
;; decisions for all devices (by default). So, we make on drawing unit in
;; a printing context match the relative drawing unit for the screen.
(define SCREEN-DPI (let ([hdc (GetDC #f)])
(begin0
(exact->inexact (GetDeviceCaps hdc LOGPIXELSX))
(ReleaseDC #f hdc))))
(define printer-dc%
(class (record-dc-mixin (dc-mixin bitmap-dc-backend%))
(init [parent #f])
@ -134,9 +147,9 @@
(let ([scale (if (zero? (bitwise-and (PAGESETUPDLG-Flags page-setup)
PSD_INTHOUSANDTHSOFINCHES))
;; 100ths of mm
(/ 72.0 (/ 10.0 2.54))
(/ SCREEN-DPI (/ 10.0 2.54))
;; 1000ths of in
(/ 72.0 1000.0))])
(/ SCREEN-DPI 1000.0))])
(values
(* scale (POINT-x (PAGESETUPDLG-ptPaperSize page-setup)))
(* scale (POINT-y (PAGESETUPDLG-ptPaperSize page-setup))))))
@ -206,14 +219,9 @@
(EndDoc hdc))
(DeleteDC hdc))))))))
(define-gdi32 GetDeviceCaps (_wfun _HDC _int -> _int))
(define LOGPIXELSX 88)
(define LOGPIXELSY 90)
(define (set-point-scale hdc cr)
(let* ([lpx (GetDeviceCaps hdc LOGPIXELSX)]
[lpy (GetDeviceCaps hdc LOGPIXELSY)]
[lx (/ (if (zero? lpx) 300 lpx) 72.0)]
[ly (/ (if (zero? lpy) 300 lpy) 72.0)])
[lx (/ (if (zero? lpx) 300 lpx) SCREEN-DPI)]
[ly (/ (if (zero? lpy) 300 lpy) SCREEN-DPI)])
(cairo_scale cr lx ly)))