[effects/zoom] Set wrap mode for cursor texture

Summary:
With the Oxygen cursor theme, a visual glitch can appear in the
bottom-left corner of the cursor when the screen is zoomed in.

The reason for that is we're using GL_REPEAT for GL_TEXTURE_WRAP_S
and GL_TEXTURE_WRAP_T. So, when the linear filter samples neighboring
texels in the bottom, it can sample some texels from the top (because of
GL_REPEAT).

To fix that, we have to set the wrap mode to GL_CLAMP_TO_EDGE.

BUG: 338254
FIXED-IN: 5.14.0

Test Plan:
Before:
{F6303912}

After:
{F6303913}

Tried other cursor themes(Breeze and Adwaita), everything looks okay.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: davidedmundson, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D15949

effects/zoom/zoom.cpp

@@ -192,8 +192,10 @@ void ZoomEffect::recreateTexture()
         imageWidth = cursor.image().width();
         imageHeight = cursor.image().height();
         cursorHotSpot = cursor.hotSpot();
-        if (effects->isOpenGLCompositing())
+        if (effects->isOpenGLCompositing()) {
             texture.reset(new GLTexture(cursor.image()));
+            texture->setWrapMode(GL_CLAMP_TO_EDGE);
+        }
 #ifdef KWIN_HAVE_XRENDER_COMPOSITING
         if (effects->compositingType() == XRenderCompositing)
             xrenderPicture.reset(new XRenderPicture(cursor.image()));