[ign-common3] Support fuel URLs for textures (#102)

Resolves gazebosim/gz-sim#343

Signed-off-by: John Shepherd <john@openrobotics.org>
Signed-off-by: Michael Carroll <michael@openrobotics.org>

graphics/src/Material.cc

@@ -144,16 +144,23 @@ void Material::SetTextureImage(const std::string &_tex)
 void Material::SetTextureImage(const std::string &_tex,
                                const std::string &_resourcePath)
 {
-  this->dataPtr->texImage = _resourcePath + "/" + _tex;
+  this->dataPtr->texImage = common::joinPaths(_resourcePath, _tex);
 
   // If the texture image doesn't exist then try the next most likely path.
   if (!exists(this->dataPtr->texImage))
   {
-    this->dataPtr->texImage = _resourcePath + "/../materials/textures/" + _tex;
+    // Try to resolve this texture image to a locally cached path in a
+    // separate directory
+    this->dataPtr->texImage = common::findFile(_tex);
     if (!exists(this->dataPtr->texImage))
     {
-      ignerr << "Unable to find texture[" << _tex << "] in path["
-            << _resourcePath << "]\n";
+      this->dataPtr->texImage = common::joinPaths(_resourcePath, "..",
+          "materials", "textures", _tex);
+      if (!exists(this->dataPtr->texImage))
+      {
+        ignerr << "Unable to find texture [" << _tex << "] as a locally"
+              " cached texture or in path ["<< _resourcePath << "]\n";
+      }
     }
   }
 }

graphics/src/Material_TEST.cc

@@ -16,6 +16,7 @@
 
 #include <gtest/gtest.h>
 
+#include "test_config.h"
 #include "ignition/common/Material.hh"
 #include "ignition/common/Pbr.hh"
 #include "test/util.hh"
@@ -35,8 +36,15 @@ TEST_F(MaterialTest, Material)
   EXPECT_STREQ("texture_image", mat.TextureImage().c_str());
 
   mat.SetTextureImage("texture_image", "/path");
-  EXPECT_STREQ("/path/../materials/textures/texture_image",
-               mat.TextureImage().c_str());
+  std::string texturePath = common::joinPaths("/path", "..",
+      "materials", "textures", "texture_image");
+  EXPECT_STREQ(texturePath.c_str(), mat.TextureImage().c_str());
+
+  texturePath = common::joinPaths(std::string(PROJECT_SOURCE_PATH), "test",
+      "data", "box.dae");
+
+  mat.SetTextureImage(texturePath, "bad_path");
+  EXPECT_STREQ(texturePath.c_str(), mat.TextureImage().c_str());
 
   mat.SetAmbient(math::Color(0.1f, 0.2f, 0.3f, 0.4f));
   EXPECT_TRUE(mat.Ambient() == math::Color(0.1f, 0.2f, 0.3f, 0.4f));