Mesa (main): wgl: rename force-msaa env-var

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Module: Mesa
Branch: main
Commit: 116553b554f501846241c9d8d1dc6e43010c85a6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=116553b554f501846241c9d8d1dc6e43010c85a6

Author: Erik Faye-Lund <erik.faye-lund at collabora.com>
Date:   Mon Mar 21 11:09:51 2022 +0100

wgl: rename force-msaa env-var

This env-var is not specific to the SVGA driver, so we should rename it
for consistency.

While we're at it, let's document the feature.

Reviewed-by: Louis-Francis Ratté-Boulianne <lfrb at collabora.com>
Reviewed-by: Jesse Natalie <jenatali at microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15485>

---

 docs/envvars.rst                            | 10 ++++++++++
 src/gallium/frontends/wgl/stw_pixelformat.c | 12 +++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/docs/envvars.rst b/docs/envvars.rst
index b8f5efb915a..39aea445b13 100644
--- a/docs/envvars.rst
+++ b/docs/envvars.rst
@@ -226,6 +226,16 @@ the :doc:`Xlib software driver page <xlibdriver>` for details.
 :envvar:`MESA_GLX_ALPHA_BITS`
    specifies default number of bits for alpha channel.
 
+Mesa WGL driver environment variables
+-------------------------------------
+
+The following are only applicable to the Mesa WGL driver, which is in use
+on Windows.
+
+:envvar:`WGL_FORCE_MSAA`
+   if set to a positive value, specifies the number of MSAA samples to
+   force when choosing the display configuration.
+
 Intel driver environment variables
 ----------------------------------------------------
 
diff --git a/src/gallium/frontends/wgl/stw_pixelformat.c b/src/gallium/frontends/wgl/stw_pixelformat.c
index 5eabd24b42d..3994ab0766c 100644
--- a/src/gallium/frontends/wgl/stw_pixelformat.c
+++ b/src/gallium/frontends/wgl/stw_pixelformat.c
@@ -252,7 +252,17 @@ add_color_format_variants(const struct stw_pf_color_info *color_formats,
     * to force all pixel formats to have a particular number of samples.
     */
    {
-      const char *samples= getenv("SVGA_FORCE_MSAA");
+      const char *samples = getenv("WGL_FORCE_MSAA");
+      if (!samples) {
+         static bool warned = false;
+         samples = getenv("SVGA_FORCE_MSAA");
+         if (samples && !warned) {
+            fprintf(stderr, "*** SVGA_FORCE_MSAA is deprecated; "
+                    "use WGL_FORCE_MSAA instead ***\n");
+            warned = true;
+         }
+      }
+
       if (samples)
          force_samples = atoi(samples);
    }