PROJ_DEBUG: make ON an alias of 2, and OFF of 1 (fixes #3832)

docs/source/usage/environmentvars.rst

@@ -69,9 +69,17 @@ done by setting the variable with no content::
 
 .. envvar:: PROJ_DEBUG
 
-    Set the debug level of PROJ. The default debug level is zero, which results
-    in no debug output when using PROJ. A number from 1-3, with 3 being the most
-    verbose setting.
+    Set the debug level of PROJ.
+
+    The following levels are available:
+    - ``0``: no message.
+    - ``1``: error messages only (default).
+    - ``2``: same as 1, with debug messages.
+    - ``3``: same as 2, with verbose messages.
+    - ``4``: same as 3, with very verbose messages.
+
+    Starting with PROJ 9.3, ``ON`` can be used as an alias for ``2``,
+    and ``OFF`` as an alias for ``1``.
 
 .. envvar:: PROJ_NETWORK
 

src/ctx.cpp

@@ -35,6 +35,7 @@
 #include <new>
 
 #include "filemanager.hpp"
+#include "proj/internal/internal.hpp"
 #include "proj/internal/io_internal.hpp"
 #include "proj_experimental.h"
 #include "proj_internal.h"
@@ -88,11 +89,25 @@ pj_ctx pj_ctx::createDefault() {
 
     const char *projDebug = getenv("PROJ_DEBUG");
     if (projDebug != nullptr) {
-        const int debugLevel = atoi(projDebug);
-        if (debugLevel >= -PJ_LOG_TRACE)
-            ctx.debug_level = debugLevel;
-        else
-            ctx.debug_level = PJ_LOG_TRACE;
+        if (NS_PROJ::internal::ci_equal(projDebug, "ON")) {
+            ctx.debug_level = PJ_LOG_DEBUG;
+        } else if (NS_PROJ::internal::ci_equal(projDebug, "OFF")) {
+            ctx.debug_level = PJ_LOG_ERROR;
+        } else if (projDebug[0] == '-' ||
+                   (projDebug[0] >= '0' && projDebug[0] <= '9')) {
+            const int debugLevel = atoi(projDebug);
+            // Negative debug levels mean that we first start logging when errno
+            // is set Cf
+            // https://github.com/OSGeo/PROJ/commit/1c1d04b45d76366f54e104f9346879fd48bfde8e
+            // This isn't documented for now. Not totally sure we really want
+            // that...
+            if (debugLevel >= -PJ_LOG_TRACE)
+                ctx.debug_level = debugLevel;
+            else
+                ctx.debug_level = PJ_LOG_TRACE;
+        } else {
+            fprintf(stderr, "Invalid value for PROJ_DEBUG: %s\n", projDebug);
+        }
     }
 
     return ctx;

src/grids.cpp

@@ -3462,19 +3462,19 @@ static PJ_LP pj_hgrid_apply_internal(PJ_CONTEXT *ctx, PJ_LP in,
                      toltol)); /* prob. slightly faster than hypot() */
 
     if (i == 0) {
-        /* If we had access to a context, this should go through pj_log, and we
-         * should set ctx->errno */
-        if (getenv("PROJ_DEBUG"))
-            fprintf(stderr,
-                    "Inverse grid shift iterator failed to converge.\n");
+        pj_log(ctx, PJ_LOG_TRACE,
+               "Inverse grid shift iterator failed to converge.\n");
+        proj_context_errno_set(ctx, PROJ_ERR_COORD_TRANSFM_OUTSIDE_GRID);
         t.lam = t.phi = HUGE_VAL;
         return t;
     }
 
     /* and again: pj_log and ctx->errno */
-    if (del.lam == HUGE_VAL && getenv("PROJ_DEBUG"))
-        fprintf(stderr, "Inverse grid shift iteration failed, presumably at "
-                        "grid edge.\nUsing first approximation.\n");
+    if (del.lam == HUGE_VAL) {
+        pj_log(ctx, PJ_LOG_TRACE,
+               "Inverse grid shift iteration failed, presumably at "
+               "grid edge.\nUsing first approximation.\n");
+    }
 
     in.lam = adjlon(t.lam + extent->west);
     in.phi = t.phi + extent->south;