SDL2 TTF font renderering, fist try.

MIvanchev · MIvanchev · commit cb4c373aa99a · 2025-04-11T18:28:59.000+02:00
diff --git a/README.org b/README.org
@@ -129,6 +129,7 @@ Advertise your module here, open a PR and include a org-mode link!
 - [[./util/productivity/README.org][productivity]] :: Lock StumpWM down so you have to get work done.
 - [[./util/qubes/README.org][qubes]] :: Integration to Qubes OS (https://www.qubes-os.org)
 - [[./util/screenshot/README.org][screenshot]] :: Takes screenshots and stores them as png files
+- [[./util/sdl2-fonts/README.md ./util/sdl2-fonts/README.txt][sdl2-fonts]] :: SDL2-based TTF font rendering for StumpWM.
 - [[./util/searchengines/README.org][searchengines]] :: Allows searching text using prompt or clipboard contents with various search engines
 - [[./util/shell-command-history/README.org][shell-command-history]] :: Save and load the stumpwm::*input-shell-history* to a file
 - [[./util/spatial-groups/README][spatial-groups]] :: Spatial Groups navigation for StumpWM
diff --git a/util/sdl-fonts/README.md b/util/sdl-fonts/README.md
@@ -0,0 +1,33 @@
+A TTF renderer for StumpWM which uses SDL. SDL is actively developed by the
+whole world so the TTF code is hopefully good as well.
+
+This module requires the native packages SDL2, SDL2_ttf and libffi.
+Make sure they are installed.
+
+Load a font through by
+
+```
+(defparameter *the-font* (sdl-fonts:load-font "/usr/share/fonts/TTF/DroidSansMono.ttf" 14))
+```
+
+And use it through
+
+```
+(set-font *the-font*)
+```
+
+Of course you can also use multiple fonts. If you want you can also set the
+hinting through
+
+```
+(defparameter *the-font* (sdl-fonts:load-font "/usr/share/fonts/TTF/DroidSansMono.ttf" 14 :hinting <hinting>))
+```
+
+where `<hinting>` is one of `:normal`, `:light`, `:mono`, `:none`, `:light-subpixel`.
+
+Have fun!
+
+Use at your own risk and discretion. I assume no responsibility for any damage
+resulting from using this project. I do use it myself.
+
+This modules borrows ideas and code from clx-truetype.
diff --git a/util/sdl-fonts/package.lisp b/util/sdl-fonts/package.lisp
@@ -0,0 +1,24 @@
+;;;; package.lisp
+
+(defpackage #:sdl-fonts
+  (:use #:cl))
+
+(in-package #:sdl-fonts)
+
+(import '(stumpwm::font-exists-p
+          stumpwm::open-font
+          stumpwm::close-font
+	  stumpwm::font-ascent
+          stumpwm::font-descent
+          stumpwm::text-line-width
+	  stumpwm::draw-image-glyphs
+          stumpwm::font-height
+          cffi:define-foreign-library
+          cffi:use-foreign-library
+          cffi:defcstruct
+          cffi:defcfun
+          cffi:foreign-slot-value
+          cffi:with-foreign-object
+          cffi:foreign-type-size
+          cffi:mem-ref
+          cffi:inc-pointer))
diff --git a/util/sdl-fonts/sdl-fonts.asd b/util/sdl-fonts/sdl-fonts.asd
@@ -0,0 +1,12 @@
+;;;; sdl-fonts.asd
+
+(asdf:defsystem #:sdl-fonts
+  :serial t
+  :description "SDL-based TTF font rendering for StumpWM."
+  :version "1.0.0"
+  :author "Mihail Ivanchev"
+  :license "MIT"
+  :depends-on (#:stumpwm #:cffi #:cffi-libffi)
+  :components ((:file "package")
+               (:file "sdl-fonts")))
+
diff --git a/util/sdl-fonts/sdl-fonts.lisp b/util/sdl-fonts/sdl-fonts.lisp
@@ -0,0 +1,260 @@
+;;;; sdl-fonts.lisp
+
+(in-package #:sdl-fonts)
+
+(export '(load-font
+          font-exists-p
+          open-font
+          close-font
+          font-ascent
+          font-descent
+          font-height
+          text-line-width
+          draw-image-glyphs))
+
+(define-foreign-library libsdl2
+  (:unix (:or "libSDL2-2.0.so.0" "libSDL2.so.0.2" "libSDL2")))
+
+(define-foreign-library libsdl2-ttf
+  (:unix (:or "libSDL2_ttf-2.0.so.0" "libSDL2_ttf")))
+
+(use-foreign-library libsdl2)
+(use-foreign-library libsdl2-ttf)
+
+(defcstruct sdl-rect
+  (x :int)
+  (y :int)
+  (w :int)
+  (h :int))
+
+(defcstruct sdl-surface
+  (flags :uint32)
+  (format :pointer)
+  (w :int)
+  (h :int)
+  (pitch :int)
+  (pixels :pointer)
+  (userdata :pointer)
+  (locked :int)
+  (list-bitmap :pointer)
+  (clip-rect (:struct sdl-rect))
+  (map :pointer)
+  (refcount :int))
+
+(defcstruct sdl-color
+  (r :uint8)
+  (g :uint8)
+  (b :uint8)
+  (a :uint8))
+
+(defvar *hinting-flags* '(:normal :light :mono :light-subpixel))
+
+(defcfun "SDL_Init" :int (flags :long))
+(defcfun "SDL_WasInit" :int (flags :long))
+(defcfun "SDL_LockSurface" :void (surf :pointer))
+(defcfun "SDL_UnlockSurface" :void (surf :pointer))
+(defcfun "SDL_FreeSurface" :void (surf :pointer))
+(defcfun "TTF_Init" :int)
+(defcfun "TTF_WasInit" :int)
+(defcfun "TTF_OpenFont" :pointer (file :string) (ptsize :int))
+(defcfun "TTF_SizeUTF8" :int (font :pointer)
+                             (text :string)
+                             (w :pointer)
+                             (h :pointer))
+(defcfun "TTF_RenderUTF8_Blended" :pointer
+                                  (font :pointer)
+                                  (text :string)
+                                  (fg (:struct sdl-color)))
+(defcfun "TTF_FontAscent" :int (font :pointer))
+(defcfun "TTF_FontDescent" :int (font :pointer))
+(defcfun "TTF_FontHeight" :int (font :pointer))
+(defcfun "TTF_SetFontSizeDPI" :int (font :pointer)
+                              (ptsize :int)
+                              (hdpi :unsigned-int)
+                              (vdpi :unsigned-int))
+(defcfun "TTF_SetFontHinting" :int (font :pointer) (hinting :int))
+
+(defclass font ()
+  ((sdl2-ptr
+     :initarg :sdl2-ptr
+     :accessor sdl2-ptr)
+   (size
+     :initarg :size
+     :accessor font-size)
+   (hdpi
+     :initform nil
+     :accessor font-hdpi)
+   (vdpi
+     :initform nil
+     :accessor font-vdpi)))
+
+(defconstant SDL_INIT_VIDEO #x00000020)
+
+(defun load-font (path size &key hinting)
+  (assert (or (not hinting) (member hinting *hinting-flags*)))
+  (when (zerop (sdl-wasinit SDL_INIT_VIDEO))
+    (sdl-init SDL_INIT_VIDEO))
+  (when (zerop (ttf-wasinit))
+    (ttf-init))
+  (let ((font (make-instance 'font
+                             :sdl2-ptr (ttf-openfont path size)
+                             :size size)))
+    (when hinting
+      (ttf-setfonthinting (sdl2-ptr font)
+                          (position hinting *hinting-flags*)))
+    font))
+
+(defmethod font-exists-p ((font font))
+  t)
+
+(defmethod open-font (display (font font))
+  font)
+
+(defmethod close-font ((font font))
+  t)
+
+(defmethod font-ascent ((font font))
+  (ttf-fontascent (sdl2-ptr font)))
+
+(defmethod font-descent ((font font))
+  (ttf-fontdescent (sdl2-ptr font)))
+
+(defmethod font-height ((font font))
+  (ttf-fontheight (sdl2-ptr font)))
+
+(defmethod text-line-width ((font font) text &rest keys &key (start 0) end translate)
+  (declare (ignorable keys start end translate))
+  (with-foreign-object (sizes :int 2)
+                       (ttf-sizeutf8
+                         (sdl2-ptr font)
+                         text
+                         sizes
+                         (inc-pointer sizes (foreign-type-size :int)))
+                       (mem-ref sizes :int 0)))
+
+(defun get-destination-picture (drawable)
+  (or (getf (xlib:drawable-plist drawable) :ttf-surface)
+      (setf (getf (xlib:drawable-plist drawable) :ttf-surface)
+            (xlib:render-create-picture
+              drawable
+              :format (first (xlib::find-matching-picture-formats (xlib:drawable-display drawable)
+                                                                  :depth (xlib:drawable-depth drawable)))))))
+(defun get-source-pixmap (drawable)
+  (or (getf (xlib:drawable-plist drawable) :ttf-pen-surface)
+      (setf (getf (xlib:drawable-plist drawable) :ttf-pen-surface)
+            (xlib:create-pixmap
+              :drawable drawable
+              :depth (xlib:drawable-depth drawable)
+              :width 1 :height 1))))
+
+(defun get-source-picture (drawable)
+  (or (getf (xlib:drawable-plist drawable) :ttf-pen)
+      (setf (getf (xlib:drawable-plist drawable) :ttf-pen)
+            (xlib:render-create-picture
+              (get-source-pixmap drawable)
+              :format (first (xlib::find-matching-picture-formats (xlib:drawable-display drawable)
+                                                                  :depth (xlib:drawable-depth drawable)))
+              :repeat :on))))
+
+(defun display-alpha-picture-format (display)
+  (or (getf (xlib:display-plist display) :ttf-alpha-format)
+      (setf (getf (xlib:display-plist display) :ttf-alpha-format)
+            (first
+              (xlib:find-matching-picture-formats
+                display
+                :depth 8 :alpha 8 :red 0 :blue 0 :green 0)))))
+
+(defun drawable-screen (drawable)
+  (typecase drawable
+    (xlib:drawable
+      (dolist (screen (xlib:display-roots (xlib:drawable-display drawable)))
+        (when (xlib:drawable-equal (xlib:screen-root screen) (xlib:drawable-root drawable))
+          (return screen))))
+    (xlib:screen drawable)
+    (t nil)))
+
+(defun screen-default-dpi (screen)
+  "Returns default dpi for @var{screen}. pixel width * 25.4/millimeters width"
+  (values (floor (* (xlib:screen-width screen) 25.4)
+                 (xlib:screen-width-in-millimeters screen))
+          (floor (* (xlib:screen-height screen) 25.4)
+                 (xlib:screen-height-in-millimeters screen))))
+
+(defun update-dpi (font drawable)
+  (multiple-value-bind (hdpi vdpi) (screen-default-dpi (drawable-screen drawable))
+    (when (or (not (eq (font-hdpi font) hdpi))
+              (not (eq (font-vdpi font) vdpi)))
+      (ttf-setfontsizedpi (sdl2-ptr font) (font-size font) hdpi vdpi)
+      (setf (font-hdpi font) hdpi)
+      (setf (font-vdpi font) vdpi))))
+
+(defmethod draw-image-glyphs (drawable
+                               gcontext
+                               (font font)
+                               x y
+                               sequence &rest keys
+                               &key (start 0) end translate width size)
+  (declare (ignorable keys start end translate width size))
+  ; Update the DPI in case it has changed (i.e. rendering to another screen).
+  (update-dpi font drawable)
+  ; This is ugly code but the idea is that we don't really know anything about
+  ; the color format etc. of the thing we are drawing on (i.e. the screen). So
+  ; we use the alpha channel of the rendered glyphs to stencil out a rectangle
+  ; in the foreground color onto a rectangle of the background color. This is
+  ; the only way to properly handle all possible cases.
+  (let* ((surf (ttf-renderutf8-blended
+                 (sdl2-ptr font)
+                 sequence
+                 '(r 0 b 0 g 0 a 0)))
+         (width (foreign-slot-value surf '(:struct sdl-surface) 'w))
+         (height (foreign-slot-value surf '(:struct sdl-surface) 'h))
+         (pitch (foreign-slot-value surf '(:struct sdl-surface) 'pitch))
+         (data (make-array (list height width) :element-type '(unsigned-byte 8))))
+    (sdl-locksurface surf)
+    (let ((pixels (foreign-slot-value surf '(:struct sdl-surface) 'pixels)))
+      (dotimes (jj height)
+        (dotimes (ii width)
+          (let ((alpha (mem-ref pixels :uint8 (+ (* jj pitch) (* ii 4) 3))))
+            (setf (aref data jj ii) alpha)))))
+    (sdl-unlocksurface surf)
+    (sdl-freesurface surf)
+    (let* ((display (xlib:drawable-display drawable))
+           (image (xlib:create-image
+                    :depth 8
+                    :width width
+                    :height height
+                    :data data))
+           (alpha-pixmap (xlib:create-pixmap :width width
+                                             :height height
+                                             :depth 8
+                                             :drawable drawable))
+           (alpha-gc (xlib:create-gcontext :drawable alpha-pixmap))
+           (alpha-pic
+             (progn
+               (xlib:put-image alpha-pixmap alpha-gc image :x 0 :y 0)
+               (xlib:render-create-picture alpha-pixmap
+                                           :format (display-alpha-picture-format display))))
+           (src-pic (get-source-picture drawable))
+           (dst-pic (get-destination-picture drawable)))
+      (xlib:free-gcontext alpha-gc)
+      ; Paint the source & destination surfaces in the foreground and
+      ; background colors of the context.
+      (xlib:draw-point (get-source-pixmap drawable) gcontext 0 0)
+      (let ((fg (xlib:gcontext-foreground gcontext)))
+        (setf (xlib:gcontext-foreground gcontext) (xlib:gcontext-background gcontext))
+        (xlib:draw-rectangle drawable gcontext x (- y (font-ascent font)) width height t)
+        (setf (xlib:gcontext-foreground gcontext) fg))
+      (xlib:render-composite :over
+                             src-pic
+                             alpha-pic
+                             dst-pic
+                             0
+                             0
+                             0
+                             0
+                             x
+                             (- y (font-ascent font))
+                             width
+                             height)
+      (xlib:render-free-picture alpha-pic)
+      (xlib:free-pixmap alpha-pixmap))))
