diff --git a/gaart.scm b/gaart.scm
index ea3db8e..b58b3d3 100644
--- a/gaart.scm
+++ b/gaart.scm
@@ -57,7 +57,7 @@
 (define (char ch)
   (define grapheme (char->grapheme ch))
   (unless grapheme
-    (scm-error #f "char" "Unable to convert ~s to a valid unicode grapheme" (list ch) (list ch)))
+    (scm-error 'convert-failure "char" "Unable to convert ~s to a valid unicode grapheme" (list ch) (list ch)))
 
   (gaart
    1 1
@@ -98,7 +98,7 @@
   (match-let ((($ <gaart> xw xh _) x))
     (unless (and (<= (+ xw cpos) matte-width)
                  (<= (+ xh rpos) matte-height))
-      (scm-error #f "matte-at" "Original (~ax~a@~a,~a) must fit inside matte (~ax~a)" (list xw xh cpos rpos matte-width matte-height) (list x)))
+      (scm-error 'matte-error "matte-at" "Original (~ax~a@~a,~a) must fit inside matte (~ax~a)" (list xw xh cpos rpos matte-width matte-height) (list x)))
     (place-at (blank matte-width matte-height) rpos cpos x)))
 
 (define* (matte matte-width matte-height x #:key (halign 'center) (valign 'center))
@@ -107,7 +107,7 @@
   (match-let ((($ <gaart> xw xh draw-x) x))
     (unless (and (<= xw width)
                  (<= xh height))
-      (scm-error #f "matte" "Original (~ax~a) must fit inside matte (~ax~a)" (list xw xh width height) (list x)))
+      (scm-error 'matte-error "matte" "Original (~ax~a) must fit inside matte (~ax~a)" (list xw xh width height) (list x)))
 
     (matte-at width height
               (match halign
@@ -189,7 +189,7 @@
   (match-let ((($ <gaart> xw xh draw-x) x)
               (($ <gaart> yw yh draw-y) y))
     (unless (= xw yw)
-      (scm-error #f "vappend2" "Widths must be equal: ~a vs ~a" (list xw yw) (list xw yw)))
+      (scm-error 'append-error "vappend2" "Widths must be equal: ~a vs ~a" (list xw yw) (list xw yw)))
     (gaart
      xw (+ xh yh)
      (λ (okay? blit! rpos cpos)
@@ -220,7 +220,7 @@
   (match-let ((($ <gaart> xw xh draw-x) x)
               (($ <gaart> yw yh draw-y) y))
     (unless (= xh yh)
-      (scm-error #f "happend2" "Heights must be equal: ~a vs ~a" (list xh yh) (list xh yh)))
+      (scm-error 'append-error "happend2" "Heights must be equal: ~a vs ~a" (list xh yh) (list xh yh)))
     (gaart
      (+ xw yw) xh
      (λ (okay? blit! rpos cpos)
@@ -230,6 +230,7 @@
            (or (dy) (dx))
            (or (dx) (dy)))))))
 
+;; TODO: for both v and h: need to better detect and error if the alignments are not set and are needed.
 (define* (happend2 y x #:key (valign #f) (reverse? #f))
   (cond
    ((not valign) (*happend2 y x #:reverse? reverse?))