Add appendPrecisionModifier method to GrGLSLShaderBuilder

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1881513002

Review URL: https://codereview.chromium.org/1881513002

4 files changed, 31 insertions, 19 deletions

diff --git a/src/gpu/glsl/GrGLSL.h b/src/gpu/glsl/GrGLSL.h
index 12c1f1fcc6..9f5f2b05b4 100644
--- a/src/gpu/glsl/GrGLSL.h
+++ b/src/gpu/glsl/GrGLSL.h
@@ -84,6 +84,23 @@ void GrGLSLAppendDefaultFloatPrecisionDeclaration(GrSLPrecision,
                                                   SkString* out);
 
 /**
+ * Converts a GrSLPrecision to its corresponding GLSL precision qualifier.
+ */
+static inline const char* GrGLSLPrecisionString(GrSLPrecision p) {
+    switch (p) {
+        case kLow_GrSLPrecision:
+            return "lowp";
+        case kMedium_GrSLPrecision:
+            return "mediump";
+        case kHigh_GrSLPrecision:
+            return "highp";
+        default:
+            SkFAIL("Unexpected precision type.");
+            return "";
+    }
+}
+
+/**
  * Converts a GrSLType to a string containing the name of the equivalent GLSL type.
  */
 static inline const char* GrGLSLTypeString(GrSLType t) {
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.cpp b/src/gpu/glsl/GrGLSLShaderBuilder.cpp
index 93b9f8a57a..795e5cb585 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.cpp
@@ -35,6 +35,12 @@ void GrGLSLShaderBuilder::declAppend(const GrGLSLShaderVar& var) {
     this->codeAppendf("%s;", tempDecl.c_str());
 }
 
+void GrGLSLShaderBuilder::appendPrecisionModifier(GrSLPrecision precision) {
+    if (fProgramBuilder->glslCaps()->usesPrecisionModifiers()) {
+        this->codeAppendf("%s ", GrGLSLPrecisionString(precision));
+    }
+}
+
 void GrGLSLShaderBuilder::emitFunction(GrSLType returnType,
                                        const char* name,
                                        int argCnt,
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.h b/src/gpu/glsl/GrGLSLShaderBuilder.h
index 5b3a01f3e9..cddf7b2db4 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.h
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.h
@@ -93,6 +93,11 @@ public:
      */
     void declAppend(const GrGLSLShaderVar& var);
 
+    /**
+     * Appends a precision qualifier followed by a space, if relevant for the GLSL version.
+     */
+    void appendPrecisionModifier(GrSLPrecision);
+
     /** Emits a helper function outside of main() in the fragment shader. */
     void emitFunction(GrSLType returnType,
                       const char* name,
diff --git a/src/gpu/glsl/GrGLSLShaderVar.h b/src/gpu/glsl/GrGLSLShaderVar.h
index a7d7479d39..9d162ecaa4 100644
--- a/src/gpu/glsl/GrGLSLShaderVar.h
+++ b/src/gpu/glsl/GrGLSLShaderVar.h
@@ -174,8 +174,9 @@ public:
             out->append(" ");
         }
         GrSLType effectiveType = this->getType();
-        if (GrSLTypeAcceptsPrecision(effectiveType)) {
-            out->append(PrecisionString(glslCaps, fPrecision));
+        if (glslCaps->usesPrecisionModifiers() && GrSLTypeAcceptsPrecision(effectiveType)) {
+            // Desktop GLSL has added precision qualifiers but they don't do anything.
+            out->appendf("%s ", GrGLSLPrecisionString(fPrecision));
         }
         if (this->isArray()) {
             if (this->isUnsizedArray()) {
@@ -210,23 +211,6 @@ public:
                      fUseUniformFloatArrays ? "" : ".x");
     }
 
-    static const char* PrecisionString(const GrGLSLCaps* glslCaps, GrSLPrecision p) {
-        // Desktop GLSL has added precision qualifiers but they don't do anything.
-        if (glslCaps->usesPrecisionModifiers()) {
-            switch (p) {
-                case kLow_GrSLPrecision:
-                    return "lowp ";
-                case kMedium_GrSLPrecision:
-                    return "mediump ";
-                case kHigh_GrSLPrecision:
-                    return "highp ";
-                default:
-                    SkFAIL("Unexpected precision type.");
-            }
-        }
-        return "";
-    }
-
 private:
     static const char* TypeModifierString(const GrGLSLCaps* glslCaps, TypeModifier t) {
         GrGLSLGeneration gen = glslCaps->generation();