Replace the resolutions min/max with an explicit list of dpi values

Previously, we could get a min/max value but there was no guarantee that it
any value in between would actually work on the device. Some devices have a
discrete number of resolutions (e.g. 500, 1000, 2000, 2500), most others have
at least a minimum step size (so 1234 isn't a valid dpi value).

Change the min/max to a discrete list of which resolutions are supported. This
allows a UI to adjust its interface dynamically - e.g. a combobox if there are
only 3 resolutions or a slider if there are a million of them.

This is a DBus API break

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/driver-hidpp10.c

@@ -437,7 +437,7 @@ hidpp10drv_read_profile(struct ratbag_profile *profile)
 
 		min = hidpp10_dpi_table_get_min_dpi(hidpp10);
 		max = hidpp10_dpi_table_get_max_dpi(hidpp10);
-		ratbag_resolution_set_range(res, min, max);
+		ratbag_resolution_set_dpi_list_from_range(res, min, max);
 	}
 
 	ratbag_profile_for_each_button(profile, button)

src/driver-hidpp20.c

@@ -667,7 +667,9 @@ hidpp20drv_read_resolution_dpi(struct ratbag_profile *profile)
 
 			/* FIXME: retrieve the refresh rate */
 			ratbag_resolution_set_resolution(res, sensor->dpi, sensor->dpi, 0);
-			ratbag_resolution_set_range(res, sensor->dpi_min, sensor->dpi_max);
+			ratbag_resolution_set_dpi_list_from_range(res,
+								  sensor->dpi_min,
+								  sensor->dpi_max);
 
 			/* FIXME: we mark all resolutions as active because
 			 * they are from different sensors */
@@ -874,7 +876,10 @@ hidpp20drv_read_profile_8100(struct ratbag_profile *profile)
 				res->is_active = true;
 		}
 
-		ratbag_resolution_set_range(res, sensor->dpi_min, sensor->dpi_max);
+		ratbag_resolution_set_dpi_list_from_range(res,
+							  sensor->dpi_min,
+							  sensor->dpi_max);
+
 	}
 }
 

src/driver-logitech-g300.c

@@ -393,9 +393,9 @@ logitech_g300_read_profile(struct ratbag_profile *profile)
 		resolution->is_default = res->is_default;
 		resolution->is_active = res->is_default;
 
-		ratbag_resolution_set_range(resolution,
-					    LOGITECH_G300_DPI_MIN,
-					    LOGITECH_G300_DPI_MAX);
+		ratbag_resolution_set_dpi_list_from_range(resolution,
+							  LOGITECH_G300_DPI_MIN,
+							  LOGITECH_G300_DPI_MAX);
 	}
 
 	ratbag_profile_for_each_button(profile, button)

src/driver-test.c

@@ -193,7 +193,9 @@ test_read_profile(struct ratbag_profile *profile)
 		assert(res);
 		ratbag_resolution_set_resolution(res, r->xres, r->yres, r->hz);
 		if (r0->dpi_min != 0 && r0->dpi_max != 0)
-			ratbag_resolution_set_range(res, r0->dpi_min, r0->dpi_max);
+			ratbag_resolution_set_dpi_list_from_range(res,
+								  r0->dpi_min,
+								  r0->dpi_max);
 		res->is_active = r->active;
 		if (r->active)
 			active_set = true;

src/libratbag-private.h

@@ -254,8 +254,10 @@ struct ratbag_resolution {
 	void *userdata;
 	struct list link;
 	unsigned index;
-	unsigned int dpi_max;	/**< max resolution in dpi */
-	unsigned int dpi_min;	/**< min resolution in dpi */
+
+	unsigned int dpis[300];
+	size_t ndpis;
+
 	unsigned int dpi_x;	/**< x resolution in dpi */
 	unsigned int dpi_y;	/**< y resolution in dpi */
 	unsigned int hz;	/**< report rate in Hz */
@@ -473,10 +475,32 @@ ratbag_resolution_set_resolution(struct ratbag_resolution *res,
 }
 
 static inline void
-ratbag_resolution_set_range(struct ratbag_resolution *res, int min, int max)
+ratbag_resolution_set_dpi_list_from_range(struct ratbag_resolution *res,
+					  unsigned int min, unsigned int max)
 {
-	res->dpi_min = min;
-	res->dpi_max = max;
+	const unsigned int stepsize = 50;
+	bool maxed_out = false;
+
+	res->ndpis = 0;
+
+	/* FIXME: this should use an exponential approach, because who cares
+	 * about 8200 vs 8250 dpi. */
+	while (res->ndpis < ARRAY_LENGTH(res->dpis)) {
+		unsigned int dpi = min + res->ndpis * stepsize;
+
+		if (dpi > (unsigned)max) {
+			maxed_out = true;
+			break;
+		}
+
+		res->dpis[res->ndpis] = dpi;
+		res->ndpis++;
+	}
+
+	if (!maxed_out)
+		log_bug_libratbag(res->profile->device->ratbag,
+				  "%s: resolution range exceeds available space.\n",
+				  res->profile->device->name);
 }
 
 static inline void

src/libratbag.c

@@ -1122,16 +1122,19 @@ ratbag_resolution_get_dpi(struct ratbag_resolution *resolution)
 	return resolution->dpi_x;
 }
 
-LIBRATBAG_EXPORT int
-ratbag_resolution_get_dpi_maximum(struct ratbag_resolution *resolution)
+LIBRATBAG_EXPORT size_t
+ratbag_resolution_get_dpi_list(struct ratbag_resolution *resolution,
+			       unsigned int *resolutions,
+			       size_t nres)
 {
-	return resolution->dpi_max;
-}
+	_Static_assert(sizeof(*resolutions) == sizeof(*resolution->dpis), "type mismatch");
 
-LIBRATBAG_EXPORT int
-ratbag_resolution_get_dpi_minimum(struct ratbag_resolution *resolution)
-{
-	return resolution->dpi_min;
+	assert(nres > 0);
+
+	memcpy(resolutions, resolution->dpis,
+	       sizeof(unsigned int) * min(nres, resolution->ndpis));
+
+	return resolution->ndpis;
 }
 
 LIBRATBAG_EXPORT int

src/libratbag.h

@@ -843,28 +843,26 @@ ratbag_resolution_get_dpi(struct ratbag_resolution *resolution);
 /**
  * @ingroup resolution
  *
- * Get the maximum allowed resolution in DPI for the resolution mode.
+ * Get the number of resolutions in DPI available for this resolution.
+ * The list of DPI values is sorted in ascending order but may be filtered
+ * by libratbag and does not necessarily reflect all resolutions supported
+ * by the physical device.
  *
- * @param resolution A previously initialized ratbag resolution
+ * This function writes at most nres values but returns the number of
+ * DPI values available on this resolution. In other words, if it returns a
+ * number larger than nres, call it again with an array the size of the
+ * return value.
  *
- * @return The maximum resolution in dpi
- * @retval 0 The maximum resolution is unknown to libratbag
+ * @param[out] resolutions Set to the supported DPI values in ascending order
+ * @param[in] nres The number of elements in resolutions
+ *
+ * @return The number of valid items in resolutions. If the returned value
+ * is larger than nres, the list was truncated.
  */
-int
-ratbag_resolution_get_dpi_maximum(struct ratbag_resolution *resolution);
-
-/**
- * @ingroup resolution
- *
- * Get the minimum allowed resolution in DPI for the resolution mode.
- *
- * @param resolution A previously initialized ratbag resolution
- *
- * @return The minimum resolution in dpi
- * @retval 0 The minimum resolution is unknown to libratbag
- */
-int
-ratbag_resolution_get_dpi_minimum(struct ratbag_resolution *resolution);
+size_t
+ratbag_resolution_get_dpi_list(struct ratbag_resolution *resolution,
+			       unsigned int *resolutions,
+			       size_t nres);
 
 /**
  * @ingroup resolution