Fix QShaderGenerator crashing when a node port name prefixed another one

QShaderGenerator didn't handle substitutions like
`vec4 $color = mix($color1, $color2, $fac);`

Note that `$color` is a prefix to `$color1` and `$color2`. For the
substitution `QByteArray::replace` was used so if `$color` was handled
first and replaced by `v1`, `$color1` and `$color2` were never correctly
replaced and instead became `v11` and `v12` which caused a crash later
on.

Change-Id: Idaf800fdac468f33c323eb722701da5f8eb918d6
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

1 files changed, 39 insertions, 3 deletions

diff --git a/src/gui/util/qshadergenerator.cpp b/src/gui/util/qshadergenerator.cpp
index bcb985de54..7ea42a7c9a 100644
--- a/src/gui/util/qshadergenerator.cpp
+++ b/src/gui/util/qshadergenerator.cpp
@@ -42,6 +42,8 @@
 #include "qshaderlanguage_p.h"
 #include <QRegularExpression>
 
+#include <cctype>
+
 QT_BEGIN_NAMESPACE
 
 Q_LOGGING_CATEGORY(ShaderGenerator, "ShaderGenerator", QtWarningMsg)
@@ -457,6 +459,13 @@ QByteArray QShaderGenerator::createShaderCode(const QStringList &enabledLayers)
         QByteArray line = node.rule(format).substitution;
         const QVector<QShaderNodePort> ports = node.ports();
 
+        struct VariableReplacement {
+            QByteArray placeholder;
+            QByteArray variable;
+        };
+
+        QVector<VariableReplacement> variableReplacements;
+
         // Generate temporary variable names vN
         for (const QShaderNodePort &port : ports) {
             const QString portName = port.name;
@@ -472,10 +481,37 @@ QByteArray QShaderGenerator::createShaderCode(const QStringList &enabledLayers)
             if (variableIndex < 0)
                 continue;
 
-            const auto placeholder = QByteArray(QByteArrayLiteral("$") + portName.toUtf8());
-            const auto variable = QByteArray(QByteArrayLiteral("v") + QByteArray::number(variableIndex));
+            VariableReplacement replacement;
+            replacement.placeholder = QByteArrayLiteral("$") + portName.toUtf8();
+            replacement.variable = QByteArrayLiteral("v") + QByteArray::number(variableIndex);
+
+            variableReplacements.append(std::move(replacement));
+        }
+
+        int begin = 0;
+        while ((begin = line.indexOf('$', begin)) != -1) {
+            int end = begin + 1;
+            char endChar = line.at(end);
+            const int size = line.size();
+            while (end < size && (std::isalnum(endChar) || endChar == '_')) {
+                ++end;
+                endChar = line.at(end);
+            }
+
+            const int placeholderLength = end - begin;
 
-            line.replace(placeholder, variable);
+            const QByteArray variableName = line.mid(begin, placeholderLength);
+            const auto replacementIt = std::find_if(variableReplacements.cbegin(), variableReplacements.cend(),
+                                              [&variableName](const VariableReplacement &replacement) {
+                return variableName == replacement.placeholder;
+            });
+
+            if (replacementIt != variableReplacements.cend()) {
+                line.replace(begin, placeholderLength, replacementIt->variable);
+                begin += replacementIt->variable.length();
+            } else {
+                begin = end;
+            }
         }
 
         // Substitute variable names by generated vN variable names