Added IMG_GetAnimationDecoderStatus() (#611)

Author: LordOfXen

include/SDL3_image/SDL_image.h

@@ -2403,6 +2403,18 @@ extern SDL_DECLSPEC IMG_Animation * SDLCALL IMG_LoadGIFAnimation_IO(SDL_IOStream
  */
 extern SDL_DECLSPEC IMG_Animation * SDLCALL IMG_LoadWEBPAnimation_IO(SDL_IOStream *src);
 
+/**
+* An enum representing the status of the encoder and decoder.
+*/
+typedef enum IMG_AnimationDecoderStatus
+{
+	IMG_DECODER_STATUS_OK, 	            /**< Decoded the frame successfully. */
+	IMG_DECODER_STATUS_FAILED,           /**< Decoding the frame failed. Call SDL_GetError for more information. */
+	IMG_DECODER_STATUS_COMPLETE, 	    /**< No more frames available. */
+
+    IMG_DECODER_STATUS_INVALID,          /**< Invalid decoder status that does not represent any valid status. */
+} IMG_AnimationDecoderStatus;
+
 /**
  * An object representing the encoder context.
  */
@@ -2688,6 +2700,19 @@ extern SDL_DECLSPEC SDL_PropertiesID SDLCALL IMG_GetAnimationDecoderProperties(I
  */
 extern SDL_DECLSPEC bool SDLCALL IMG_GetAnimationDecoderFrame(IMG_AnimationDecoder *decoder, SDL_Surface **frame, Uint64 *duration);
 
+/**
+* Get the decoder status indicating the current state of the decoder.
+*
+* \param decoder the decoder to get the status of.
+* \returns the status of the underlying decoder, or IMG_DECODER_STATUS_INVALID if the given
+*          decoder is invalid.
+*
+* \since This function is available since SDL_image 3.4.0.
+*
+* \sa IMG_GetAnimationDecoderFrame
+*/
+extern SDL_DECLSPEC IMG_AnimationDecoderStatus SDLCALL IMG_GetAnimationDecoderStatus(IMG_AnimationDecoder *decoder);
+
 /**
  * Reset an animation decoder.
  *

src/IMG_anim_decoder.c

@@ -193,14 +193,23 @@ bool IMG_GetAnimationDecoderFrame(IMG_AnimationDecoder *decoder, SDL_Surface **f
     if (!duration) {
         duration = &temp_duration;
     }
-
     SDL_ClearError();
+    // Reset the status before trying to get the next frame.
+    decoder->status = IMG_DECODER_STATUS_OK;
 
     bool result = decoder->GetNextFrame(decoder, frame, duration);
     if (temp_frame) {
         SDL_DestroySurface(temp_frame);
     }
 
+    if (!result) {
+        if (SDL_GetError()[0] == '\0') {
+            decoder->status = IMG_DECODER_STATUS_COMPLETE;
+        } else {
+            decoder->status = IMG_DECODER_STATUS_FAILED;
+        }
+    }
+
     if (result) {
         decoder->accumulated_pts += *duration;
     } else {
@@ -242,12 +251,22 @@ bool IMG_ResetAnimationDecoder(IMG_AnimationDecoder *decoder)
 
 Uint64 IMG_CalculateDuration(IMG_AnimationDecoder* decoder, int delay_num, int delay_den)
 {
-    if (delay_den < 1)
+    if (delay_den < 1) {
         delay_den = 100;
+    }
 
     return (Uint64)SDL_round(((double)delay_num / delay_den) * ((double)decoder->timebase_denominator / (double)decoder->timebase_numerator));
 }
 
+IMG_AnimationDecoderStatus IMG_GetAnimationDecoderStatus(IMG_AnimationDecoder* decoder)
+{
+    if (!decoder) {
+        return IMG_DECODER_STATUS_INVALID;
+    }
+
+    return decoder->status;
+}
+
 IMG_Animation *IMG_DecodeAsAnimation(SDL_IOStream *src, const char *format, int maxFrames)
 {
     IMG_AnimationDecoder *decoder = IMG_CreateAnimationDecoder_IO(src, false, format);

src/IMG_anim_decoder.h

@@ -23,6 +23,7 @@ typedef struct IMG_AnimationDecoderContext IMG_AnimationDecoderContext;
 
 struct IMG_AnimationDecoder
 {
+    IMG_AnimationDecoderStatus status;
     SDL_PropertiesID props;
     SDL_IOStream *src;
     Sint64 start;

src/IMG_anim_encoder.c

@@ -171,11 +171,12 @@ bool IMG_AddAnimationEncoderFrame(IMG_AnimationEncoder *encoder, SDL_Surface *su
     if (!surface || surface->w <= 0 || surface->h <= 0) {
         return SDL_InvalidParamError("surface");
     }
-
     bool result = encoder->AddFrame(encoder, surface, duration);
 
-    encoder->accumulated_pts += duration;
-    encoder->last_delay = duration;
+    if (result) {
+        encoder->accumulated_pts += duration;
+        encoder->last_delay = duration;
+    }
 
     return result;
 }

src/IMG_webp.c

@@ -448,8 +448,9 @@ static bool IMG_AnimationDecoderGetNextFrame_Internal(IMG_AnimationDecoder *deco
     int totalFrames = decoder->ctx->iter.num_frames;
     int availableFrames = totalFrames - (decoder->ctx->iter.frame_num - 1);
 
-    if (availableFrames < 1)
+    if (availableFrames < 1) {
         return false;
+    }
 
     SDL_Surface *canvas = decoder->ctx->canvas;
     uint32_t bgcolor = decoder->ctx->bgcolor;

src/SDL_image.sym

@@ -83,5 +83,6 @@ SDL3_image_0.0.0 {
     IMG_ResetAnimationDecoder;
     IMG_CloseAnimationDecoder;
     IMG_GetAnimationDecoderProperties;
+    IMG_GetAnimationDecoderStatus;
   local: *;
 };