Do not hardcode backdrop numbers and filenames. Allow all backdrop types to have

random variations, based on filename base. Hardcoded limits removed. Patch by stiv,
modified by me. Closes ticket:4168

lib/ivis_opengl/pieblitfunc.cpp

@@ -42,6 +42,7 @@
 #include "piematrix.h"
 #include "screen.h"
 
+
 /***************************************************************************/
 /*
  *	Local Variables
@@ -463,27 +464,19 @@ void pie_RenderRadar()
 	radarGfx->draw();
 }
 
+/// Load and display a random backdrop picture.
 void pie_LoadBackDrop(SCREENTYPE screenType)
 {
-	char backd[128];
-
-	//randomly load in a backdrop piccy.
-	srand( (unsigned)time(NULL) + 17 ); // Use offset since time alone doesn't work very well
-
 	switch (screenType)
 	{
-		case SCREEN_RANDOMBDROP:
-			snprintf(backd, sizeof(backd), "texpages/bdrops/backdrop%i.png", rand() % NUM_BACKDROPS); // Range: 0 to (NUM_BACKDROPS-1)
-			break;
-		case SCREEN_MISSIONEND:
-			sstrcpy(backd, "texpages/bdrops/missionend.png");
-			break;
-
-		case SCREEN_CREDITS:
-		default:
-			sstrcpy(backd, "texpages/bdrops/credits.png");
-			break;
+	case SCREEN_RANDOMBDROP:
+		screen_SetRandomBackdrop("texpages/bdrops/", "backdrop");
+		break;
+	case SCREEN_MISSIONEND:
+		screen_SetRandomBackdrop("textpages/bdrops/", "missionend");
+		break;
+	case SCREEN_CREDITS:
+		screen_SetRandomBackdrop("texpages/bdrops/", "credits");
+		break;
 	}
-
-	screen_SetBackDropFromFile(backd);
 }

lib/ivis_opengl/screen.cpp

@@ -49,6 +49,13 @@
 
 #include <GL/glext.h>
 
+#include <iostream>
+#include <string>
+#include <vector>
+#include <cstring>
+
+//using namespace std;
+
 /* global used to indicate preferred internal OpenGL format */
 int wz_texture_compression = 0;
 
@@ -357,6 +364,32 @@ void screenShutDown(void)
 	glErrors();
 }
 
+/// Display a random backdrop from files in dirname starting with basename.
+/// dirname must have a trailing slash.
+void screen_SetRandomBackdrop(const char *dirname, const char *basename)
+{
+	std::vector<std::string> names;  // vector to hold the strings we want
+	char **rc = PHYSFS_enumerateFiles(dirname); // all the files in dirname
+
+	// Walk thru the files in our dir, adding the ones that start with basename to our vector of strings
+	size_t len = strlen(basename);
+	for (char **i = rc; *i != NULL; i++)
+	{
+		// does our filename start with basename?
+		if (!strncmp(*i, basename, len))
+		{
+			names.push_back(*i);
+		}
+	}
+	PHYSFS_freeList(rc);
+
+	// pick a random name from our vector of names
+	int ran = rand() % names.size();
+	std::string full_path = std::string(dirname) + names[ran];
+
+	screen_SetBackDropFromFile(full_path.c_str());
+}
+
 void screen_SetBackDropFromFile(const char* filename)
 {
 	backdropGfx->loadTexture(filename);

lib/ivis_opengl/screen.h

@@ -38,10 +38,13 @@
 
 /* ------------------------------------------------------------------------------------------- */
 
+
 extern unsigned screenWidth;
 extern unsigned screenHeight;
 
 /* backDrop */
+void screen_SetRandomBackdrop( const char* dirname, 
+			       const char* basename );
 extern void screen_SetBackDropFromFile(const char* filename);
 extern void screen_StopBackDrop(void);
 extern void screen_RestartBackDrop(void);