From 1967f72de20cc0c176375b4a1b704b322ef7dcd1 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 12 Jul 2020 08:19:45 -0400
Subject: render: gpu: Query GL context for GL and GLSL versions.

---
 chickadee.scm            |  6 ++++++
 chickadee/render/gl.scm  |  7 +++++++
 chickadee/render/gpu.scm | 18 ++++++++++++++++--
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/chickadee.scm b/chickadee.scm
index defa0a0..7b43888 100644
--- a/chickadee.scm
+++ b/chickadee.scm
@@ -235,6 +235,12 @@ border is disabled, otherwise it is enabled.")
   (sdl-init)
   (start-text-input)
   (init-audio)
+  ;; Hint that we want OpenGL 3.2 Core profile.  Doesn't mean we'll
+  ;; get it, though!
+  (sdl2:set-gl-attribute! 'context-major-version 3)
+  (sdl2:set-gl-attribute! 'context-major-version 2)
+  (sdl2:set-gl-attribute! 'context-profile-mask 1) ; core profile
+  (sdl2:set-gl-attribute! 'stencil-size 8) ; 8-bit stencil buffer
   (let* ((window (sdl2:make-window #:opengl? #t
                                    #:title window-title
                                    #:size (list window-width window-height)
diff --git a/chickadee/render/gl.scm b/chickadee/render/gl.scm
index 7b23697..295a7bb 100644
--- a/chickadee/render/gl.scm
+++ b/chickadee/render/gl.scm
@@ -299,3 +299,10 @@ object.")
            (%glUniform4f .  gl-uniform4f))
 
 (re-export (%glPointSize . gl-point-size))
+
+
+;;;
+;;; Context Queries
+;;;
+
+(re-export (%glGetString . gl-get-string))
diff --git a/chickadee/render/gpu.scm b/chickadee/render/gpu.scm
index 66510fc..554e263 100644
--- a/chickadee/render/gpu.scm
+++ b/chickadee/render/gpu.scm
@@ -16,8 +16,11 @@
 ;;; <http://www.gnu.org/licenses/>.
 
 (define-module (chickadee render gpu)
+  #:use-module (chickadee render gl)
+  #:use-module (gl enums)
   #:use-module (oop goops)
   #:use-module (srfi srfi-9)
+  #:use-module (system foreign)
   #:export (make-gpu-state
             gpu-state-ref
             gpu-state-set!
@@ -30,6 +33,8 @@
             current-gpu
             gpu?
             gpu-gl-context
+            gpu-gl-version
+            gpu-glsl-version
             gpu-blend-mode
             gpu-depth-test
             gpu-framebuffer
@@ -91,6 +96,8 @@ from the GPU's memory."
 
 (define-record-type <gpu>
   (%make-gpu gl-context
+             gl-version
+             glsl-version
              blend-mode
              depth-test
              framebuffer
@@ -101,6 +108,8 @@ from the GPU's memory."
              viewport)
   gpu?
   (gl-context gpu-gl-context)
+  (gl-version gpu-gl-version)
+  (glsl-version gpu-glsl-version)
   (blend-mode %gpu-blend-mode)
   (depth-test %gpu-depth-test)
   (framebuffer %gpu-framebuffer)
@@ -113,6 +122,8 @@ from the GPU's memory."
 (define current-gpu (make-parameter #f))
 
 (define (make-gpu gl-context)
+  (define (extract-version attr)
+    (car (string-split (pointer->string (gl-get-string attr)) #\space)))
   (let ((textures (make-vector 32))
         ;; Lazily resolve bindings to avoid circular dependencies.
         (blend-module (resolve-interface '(chickadee render blend)))
@@ -120,7 +131,9 @@ from the GPU's memory."
         (framebuffer-module (resolve-interface '(chickadee render framebuffer)))
         (shader-module (resolve-interface '(chickadee render shader)))
         (texture-module (resolve-interface '(chickadee render texture)))
-        (viewport-module (resolve-interface '(chickadee render viewport))))
+        (viewport-module (resolve-interface '(chickadee render viewport)))
+        (gl-version (extract-version (string-name version)))
+        (glsl-version (extract-version (version-2-0 shading-language-version))))
     ;; Create state for 32 texture units.
     (let loop ((i 0))
       (when (< i 32)
@@ -131,7 +144,8 @@ from the GPU's memory."
                                        (module-ref texture-module 'null-texture))))
         (loop (+ i 1))))
     (%make-gpu gl-context
-               ;; Use @ and @@ to avoid circular module dependencies.
+               gl-version
+               glsl-version
                (make-gpu-state (module-ref blend-module 'apply-blend-mode)
                                'replace)
                (make-gpu-state (module-ref blend-module 'apply-depth-test)
-- 
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