rename 'disc' as 'memory'

the old 'disc' flag to open defaulted TRUE and disabled read via disc if you
set it FALSE, which was very confusing

replace it with a flag called 'memory' which defaults FALSE and forces
read via memory if set TRUE

'disc' is still there and still works, it's just tagged as deprecated

see https://github.com/jcupitt/libvips/issues/677

ChangeLog

@@ -9,6 +9,7 @@
 - add vips_thumbnail_image()
 - better prefix guessing on Windows, thanks tumagonx
 - savers support a "page_height" option for multipage save
+- rename 'disc' as 'memory' and default off
 
 12/6/17 started 8.5.7
 - transform cmyk->rgb automatically on write if there's an embedded profile

libvips/foreign/foreign.c

@@ -740,12 +740,18 @@ vips_foreign_load_temp( VipsForeignLoad *load )
 		return( vips_image_new() );
 	}
 
+	/* ->memory used to be called ->disc and default TRUE. If it's been
+	 * forced FALSE, set memory TRUE.
+	 */
+	if( !load->disc )
+		load->memory = TRUE;
+
 	/* We open via disc if:
-	 * - 'disc' is set
+	 * - 'memory' is off
 	 * - the uncompressed image will be larger than 
 	 *   vips_get_disc_threshold()
 	 */
-	if( load->disc && 
+	if( !load->memory && 
 		image_size > disc_threshold ) {
 #ifdef DEBUG
 		printf( "vips_foreign_load_temp: disc temp\n" );
@@ -997,12 +1003,12 @@ vips_foreign_load_class_init( VipsForeignLoadClass *class )
 		G_STRUCT_OFFSET( VipsForeignLoad, flags ),
 		VIPS_TYPE_FOREIGN_FLAGS, VIPS_FOREIGN_NONE ); 
 
-	VIPS_ARG_BOOL( class, "disc", 7, 
-		_( "Disc" ), 
-		_( "Open to disc" ),
+	VIPS_ARG_BOOL( class, "memory", 7, 
+		_( "Memory" ), 
+		_( "Force open via memory" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
-		G_STRUCT_OFFSET( VipsForeignLoad, disc ),
-		TRUE );
+		G_STRUCT_OFFSET( VipsForeignLoad, memory ),
+		FALSE );
 
 	VIPS_ARG_ENUM( class, "access", 8, 
 		_( "Access" ), 
@@ -1025,6 +1031,13 @@ vips_foreign_load_class_init( VipsForeignLoadClass *class )
 		G_STRUCT_OFFSET( VipsForeignLoad, fail ),
 		FALSE );
 
+	VIPS_ARG_BOOL( class, "disc", 12, 
+		_( "Disc" ), 
+		_( "Open to disc" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT | VIPS_ARGUMENT_DEPRECATED,
+		G_STRUCT_OFFSET( VipsForeignLoad, disc ),
+		TRUE );
+
 }
 
 static void

libvips/include/vips/foreign.h

@@ -119,9 +119,9 @@ typedef struct _VipsForeignLoad {
 	VipsForeign parent_object;
 	/*< private >*/
 
-	/* Open to disc (default is to open to memory).
+	/* Set TRUE to force open via memory. 
 	 */
-	gboolean disc;
+	gboolean memory;
 
 	/* Type of access upstream wants and the loader must supply. 
 	 */
@@ -153,6 +153,11 @@ typedef struct _VipsForeignLoad {
 	/* Set this to tag the operation as nocache.
 	 */
 	gboolean nocache;
+
+	/* Deprecated: the memory option used to be called disc and default
+	 * TRUE.
+	 */
+	gboolean disc;
 } VipsForeignLoad;
 
 typedef struct _VipsForeignLoadClass {

libvips/iofuncs/image.c

@@ -1831,7 +1831,7 @@ vips_filename_get_options( const char *vips_filename )
  * Optional arguments:
  *
  * * @access: hint #VipsAccess mode to loader
- * * @disc: load via a temporary disc file
+ * * @memory: force load via memory 
  *
  * vips_image_new_from_file() opens @name for reading. It can load files
  * in many image formats, including VIPS, TIFF, PNG, JPEG, FITS, Matlab,
@@ -1856,12 +1856,15 @@ vips_filename_get_options( const char *vips_filename )
  *
  * In #VIPS_ACCESS_RANDOM mode, small images are decompressed to memory and
  * then processed from there. Large images are decompressed to temporary
- * random-access files on disc and then processed from there. Set @disc to
- * %TRUE to force loading via disc. See vips_image_new_temp_file() for an 
+ * random-access files on disc and then processed from there. 
+ *
+ * Set @memory to %TRUE to force loading via memory. The default is to load 
+ * large random access images via temporary disc files. See 
+ * vips_image_new_temp_file() for an 
  * explanation of how VIPS selects a location for the temporary file.
  *
  * The disc threshold can be set with the "--vips-disc-threshold"
- * command-line argument, or the VIPS_DISC_THRESHOLD environment variable.
+ * command-line argument, or the `VIPS_DISC_THRESHOLD` environment variable.
  * The value is a simple integer, but can take a unit postfix of "k", 
  * "m" or "g" to indicate kilobytes, megabytes or gigabytes.
  * The default threshold is 100 MB.