Pretty print of shaders

src/gpu/gl/GrGLPrettyPrintSL.cpp

+#include "GrGLPrettyPrintSL.h"

[bsalomon, 2014/08/01 13:37:06]

Copyright

+// This code is terrible.  I'm sorry.  It has to be fast in addition to being correct.
+// Please do not abuse this class.  All it can do is dumbly format simple glsl.  It also can
+// optionally add line numbers.  I'm sure this will get confused with any really complex glsl stuff
+
+// rules: puts each '{' on its own line, indented properly, and matches the '}'.  It expects
+// '//' comments and '#' to end with '\n', just as the glsl spec does.  It can also accept /**/
+// style comments.  It knows about for loops also, that is the extent of its intellect.  It ignores
+// tabs and newlines aside from the aformentioned cases, so its best to avoid 'cute' formatting
+// (ie, trying to align matrix parameters).  Instead, make the glsl code look nice in Skia.
+
+// I toyed with the idea of making a true token based parser which would build an AST and could
+// more agressively format output, but this is all just a stop gap measure.
+
+// TODO in the longterm, completely revamp how we write shaders.  We shouldn't be embedding strings
+// in source code, but instead should build a language into C++ using classes and overloaded
+// operators which would allow us to express gpu algorithms in C++ directly.
+
+namespace GrGLPrettyPrintSL {
+
+static void tab_skstring(SkString& s, int tabs) {
+    for (int t = 0; t < tabs; t++) {
+        s.append("\t");
+    }
+}
+
+size_t copy_to_newline(const SkString& input, const size_t length, size_t i, SkString& pretty) {
+    while (length > i) {
+        if ('\n' == input[i]) {
+            break;
+        }
+        pretty.appendf("%c", input[i]);
+        i++;
+    }
+    return i;
+}
+
+void line_numbering(SkString& pretty, bool countlines, int linecount, int tabs) {
+    if (linecount != 1) {
+        pretty.append("\n");
+    }
+    if (countlines) {
+        pretty.appendf("%4d\t", linecount);
+    }
+    tab_skstring(pretty, tabs);
+}
+
+SkString pretty_print_sl(const SkString& input, bool countlines) {
+    SkString pretty;
+    int linecount = 1;
+    bool newline = false;
+    // for loops mess us up, so don't touch semicolons in for loops
+    int parensDepth = 0;
+    int tabs = 0;
+    size_t i = 0;
+    const size_t length = input.size();
+    while (length > i) {
+        // '//' comment or '#'
+        if ('#' == input[i] ||
+                ('/' == input[i] && length > i + 1 && '/' == input[i + 1])) {
+            line_numbering(pretty, countlines, linecount++, tabs);
+            i = copy_to_newline(input, length, i, pretty);
+            newline = true;
+        }
+
+        // /**/ comment
+        if ('/' == input[i] && length > i + 1 && '*' == input[i + 1]) {
+            line_numbering(pretty, countlines, linecount++, tabs);
+            while (length > i) {
+                pretty.appendf("%c", input[i]);
+                if ('*' == input[i] && length > i + 1 && '/' == input[i + 1]) {
+                    // eat the slash
+                    i++;
+                    pretty.appendf("%c", input[i]);
+                    break;
+                }
+                i++;
+            }
+            newline = true;
+        }
+
+        if (length <= i) {
+            break;
+        }
+
+        // ignore any pre-existing punctuation
+        if ((newline && (' ' == input[i] || '\t' == input[i] || '\n' == input[i]))
+                ||'\n' == input[i] || '\t' == input[i]) {
+            i++;
+            continue;
+        } else if ('{' == input[i]) {
+            line_numbering(pretty, countlines, linecount++, tabs);
+            pretty.append("{");
+            tabs++;
+            newline = true;
+        } else if ('}' == input[i]) {
+            tabs--;
+            line_numbering(pretty, countlines, linecount++, tabs);
+            pretty.append("}");
+            newline = true;
+        } else if (!parensDepth && ';' == input[i]) {
+            pretty.append(";");
+            newline = true;
+        } else {
+            if (newline) {
+                line_numbering(pretty, countlines, linecount++, tabs);
+                newline = false;
+            }
+            if ('(' == input[i]) {
+                parensDepth++;
+            } else if (')' == input[i]) {
+                parensDepth--;
+            }
+            pretty.appendf("%c", input[i]);
+        }
+        i++;
+    }
+    return pretty;
+}
+
+} // end namespace