Merge pull request #4381 from rouault/gtiff_grid_name_improvement

Debugging/internals: append sub-grid index to grid name when opening a multi-grid TIFF file

src/grids.cpp

@@ -1320,6 +1320,15 @@ std::unique_ptr<GTiffGrid> GTiffDataset::nextGrid() {
     m_ifdIdx++;
     m_hasNextGrid = TIFFReadDirectory(m_hTIFF) != 0;
     m_nextDirOffset = TIFFCurrentDirOffset(m_hTIFF);
+
+    // If the TIFF file contains multiple grids, append the index of the grid
+    // in the grid name to help debugging.
+    if (m_ifdIdx >= 2 || m_hasNextGrid) {
+        ret->m_name += " (index ";
+        ret->m_name += std::to_string(m_ifdIdx); // 1-based
+        ret->m_name += ')';
+    }
+
     return ret;
 }
 

src/grids.hpp

@@ -59,6 +59,7 @@ struct ExtentAndRes {
 
 class PROJ_GCC_DLL Grid {
   protected:
+    friend class GTiffDataset;
     std::string m_name;
     int m_width;
     int m_height;