Add Depth compare / shadow sampler support. Officially this is only supported in glsl3 shaders.

- Add Texture:setDepthSampleMode(comparemode). Only works on textures with depth pixel formats. A texture with the depth sample mode set will only work with a depth sampler.
- Add DepthImage, DepthArrayImage, and DepthCubeImage sampler keywords to glsl3.

--HG--
branch : minor

src/modules/graphics/depthstencil.cpp

@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) 2006-2017 LOVE Development Team
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ **/
+
+#include "depthstencil.h"
+#include "common/StringMap.h"
+
+namespace love
+{
+namespace graphics
+{
+
+CompareMode getReversedCompareMode(CompareMode mode)
+{
+	switch (mode)
+	{
+	case COMPARE_LESS:
+		return COMPARE_GREATER;
+	case COMPARE_LEQUAL:
+		return COMPARE_GEQUAL;
+	case COMPARE_EQUAL:
+		return COMPARE_EQUAL;
+	case COMPARE_GEQUAL:
+		return COMPARE_LEQUAL;
+	case COMPARE_GREATER:
+		return COMPARE_LESS;
+	case COMPARE_NOTEQUAL:
+		return COMPARE_NOTEQUAL;
+	case COMPARE_ALWAYS:
+		return COMPARE_ALWAYS;
+	case COMPARE_MAX_ENUM:
+	default:
+		return COMPARE_MAX_ENUM;
+	}
+}
+
+static StringMap<StencilAction, STENCIL_MAX_ENUM>::Entry stencilActionEntries[] =
+{
+	{ "replace",       STENCIL_REPLACE        },
+	{ "increment",     STENCIL_INCREMENT      },
+	{ "decrement",     STENCIL_DECREMENT      },
+	{ "incrementwrap", STENCIL_INCREMENT_WRAP },
+	{ "decrementwrap", STENCIL_DECREMENT_WRAP },
+	{ "invert",        STENCIL_INVERT         },
+};
+
+static StringMap<StencilAction, STENCIL_MAX_ENUM> stencilActions(stencilActionEntries, sizeof(stencilActionEntries));
+
+static StringMap<CompareMode, COMPARE_MAX_ENUM>::Entry compareModeEntries[] =
+{
+	{ "less",     COMPARE_LESS     },
+	{ "lequal",   COMPARE_LEQUAL   },
+	{ "equal",    COMPARE_EQUAL    },
+	{ "gequal",   COMPARE_GEQUAL   },
+	{ "greater",  COMPARE_GREATER  },
+	{ "notequal", COMPARE_NOTEQUAL },
+	{ "always",   COMPARE_ALWAYS   },
+};
+
+static StringMap<CompareMode, COMPARE_MAX_ENUM> compareModes(compareModeEntries, sizeof(compareModeEntries));
+
+bool getConstant(const char *in, StencilAction &out)
+{
+	return stencilActions.find(in, out);
+}
+
+bool getConstant(StencilAction in, const char *&out)
+{
+	return stencilActions.find(in, out);
+}
+
+bool getConstant(const char *in, CompareMode &out)
+{
+	return compareModes.find(in, out);
+}
+
+bool getConstant(CompareMode in, const char *&out)
+{
+	return compareModes.find(in, out);
+}
+
+} // graphics
+} // love