Merge branch 'unstable' into rettichschnidi

diff --combined src/am7xxx.c
index 30e689f,a840589..67718db
--- 1/src/am7xxx.c
--- 2/src/am7xxx.c
+++ b/src/am7xxx.c
@@@ -244,7 -244,6 +244,7 @@@ static void debug_dump_header(am7xxx_co
        (void)ctx;
        (void)h;
  }
 +
  static void trace_dump_buffer(am7xxx_context *ctx, const char *message,
                              uint8_t *buffer, unsigned int len)
  {
@@@ -691,6 -690,68 +691,68 @@@ int am7xxx_get_device_info(am7xxx_devic
        return 0;
  }
  
+ int am7xxx_calc_scaled_image_dimensions(am7xxx_device *dev,
+                                       unsigned int upscale,
+                                       unsigned int original_width,
+                                       unsigned int original_height,
+                                       unsigned int *scaled_width,
+                                       unsigned int *scaled_height)
+ {
+ 
+       am7xxx_device_info device_info;
+       float width_ratio;
+       float height_ratio;
+       int ret;
+ 
+       ret = am7xxx_get_device_info(dev, &device_info);
+       if (ret < 0) {
+               error(dev->ctx, "cannot get device info\n");
+               return ret;
+       }
+ 
+       /*
+        * Check if we need to rescale; if the input image fits the native
+        * dimensions there is no need to, unless we want to upscale.
+        */
+       if (!upscale &&
+           original_width <= device_info.native_width &&
+           original_height <= device_info.native_height ) {
+               debug(dev->ctx, "CASE 0, no rescaling, the original image fits already\n");
+               *scaled_width = original_width;
+               *scaled_height = original_height;
+               return 0;
+       }
+ 
+       /* Input dimensions relative to the device native dimensions */
+       width_ratio =  (float)original_width / device_info.native_width;
+       height_ratio = (float)original_height / device_info.native_height;
+ 
+       if (width_ratio > height_ratio) {
+               /*
+                * The input is proportionally "wider" than the device viewport
+                * so it's height needs to be adjusted
+                */
+               debug(dev->ctx, "CASE 1, original image wider, adjust the scaled height\n");
+               *scaled_width = device_info.native_width;
+               *scaled_height = (unsigned int)(original_height / width_ratio);
+       } else if (width_ratio < height_ratio) {
+               /*
+                * The input is proportionally "taller" than the device viewport
+                * so its width needs to be adjusted
+                */
+               debug(dev->ctx, "CASE 2 original image taller, adjust the scaled width\n");
+               *scaled_width = (unsigned int)(original_width / height_ratio);
+               *scaled_height = device_info.native_height;
+       } else {
+               debug(dev->ctx, "CASE 3, just rescale, same aspect ratio already\n");
+               *scaled_width = device_info.native_width;
+               *scaled_height = device_info.native_height;
+       }
+       debug(dev->ctx, "scaled dimensions: %dx%d\n", *scaled_width, *scaled_height);
+ 
+       return 0;
+ }
+ 
  int am7xxx_send_image(am7xxx_device *dev,
                      am7xxx_image_format format,
                      unsigned int width,