Forms: use a text matrix to fit text rather than altering the font size

To achieve sufficient accuracy, non-integer font sizes were being used,
which MuPDF can handle, but may be illegal. The text matrix is the better
method.

1 files changed, 21 insertions, 14 deletions

diff --git a/pdf/pdf_form.c b/pdf/pdf_form.c
index aec11a09..e7e5caec 100644
--- a/pdf/pdf_form.c
+++ b/pdf/pdf_form.c
@@ -153,7 +153,7 @@ static int read_font_size_from_da(fz_context *ctx, char *da)
 	return fontsize;
 }
 
-static void copy_da_with_altered_size(fz_context *ctx, fz_buffer *fzbuf, char *da, float size)
+static void copy_da_with_altered_size(fz_context *ctx, fz_buffer *fzbuf, char *da, int size)
 {
 	int tok;
 	pdf_lexbuf lbuf;
@@ -171,7 +171,7 @@ static void copy_da_with_altered_size(fz_context *ctx, fz_buffer *fzbuf, char *d
 			if (last_tok_was_int)
 			{
 				if (tok == PDF_TOK_KEYWORD && !strcmp(lbuf.scratch, "Tf"))
-					fz_buffer_printf(ctx, fzbuf, " %1.2f", size);
+					fz_buffer_printf(ctx, fzbuf, " %d", size);
 				else
 					fz_buffer_printf(ctx, fzbuf, " %d", last_int_tok_val);
 
@@ -223,7 +223,7 @@ static fz_bbox measure_text(pdf_document *doc, pdf_obj *dr, fz_buffer *fzbuf)
 	return bbox;
 }
 
-static fz_buffer *create_text_buffer(fz_context *ctx, fz_rect *clip, char *da, float fontsize, float x, float y, char *text)
+static fz_buffer *create_text_buffer(fz_context *ctx, fz_rect *clip, char *da, int fontsize, fz_matrix *tm, char *text)
 {
 	fz_buffer *fzbuf = fz_new_buffer(ctx, 0);
 	const char *fmtstart =
@@ -236,7 +236,7 @@ static fz_buffer *create_text_buffer(fz_context *ctx, fz_rect *clip, char *da, f
 	const char *fmtbtxt =
 		" BT";
 	const char *fmttxt =
-		" %1.2f %1.2f Td"
+		" %1.2f %1.2f %1.2f %1.2f %1.2f %1.2f Tm"
 		" (%s) Tj"
 		" ET"
 		" Q"
@@ -248,11 +248,11 @@ static fz_buffer *create_text_buffer(fz_context *ctx, fz_rect *clip, char *da, f
 		if (clip)
 			fz_buffer_printf(ctx, fzbuf, fmtclip, clip->x0, clip->y0, clip->x1 - clip->x0, clip->y1 - clip->y0);
 		fz_buffer_printf(ctx, fzbuf, fmtbtxt);
-		if (fontsize < 0.0)
+		if (fontsize < 0)
 			fz_buffer_printf(ctx, fzbuf, " %s", da); /* Copy da unchanged */
 		else
 			copy_da_with_altered_size(ctx, fzbuf, da, fontsize);
-		fz_buffer_printf(ctx, fzbuf, fmttxt, x, y, text);
+		fz_buffer_printf(ctx, fzbuf, fmttxt, tm->a, tm->b, tm->c, tm->d, tm->e, tm->f, text);
 	}
 	fz_catch(ctx)
 	{
@@ -280,7 +280,7 @@ static void measure_ascent_descent(pdf_document *doc, pdf_obj *dr, char *da, cha
 		strcpy(testtext, "My");
 		strcat(testtext, text);
 		/* Use large font size for increased accuracy */
-		fzbuf = create_text_buffer(ctx, NULL, da, 100, 0, 0, testtext);
+		fzbuf = create_text_buffer(ctx, NULL, da, 100, &fz_identity, testtext);
 		bbox = measure_text(doc, dr, fzbuf);
 		*descent = -bbox.y0 / 100.0;
 		*ascent = bbox.y1 / 100.0;
@@ -299,7 +299,8 @@ static void measure_ascent_descent(pdf_document *doc, pdf_obj *dr, char *da, cha
 fz_buffer *create_text_appearance(pdf_document *doc, fz_rect *bbox, pdf_obj *dr, char *da, char *text)
 {
 	fz_context *ctx = doc->ctx;
-	float height, width, fontsize;
+	int fontsize;
+	float height, width;
 	fz_buffer *fzbuf = NULL;
 	fz_rect rect;
 	fz_bbox tbox;
@@ -320,17 +321,22 @@ fz_buffer *create_text_appearance(pdf_document *doc, fz_rect *bbox, pdf_obj *dr,
 	fz_try(ctx)
 	{
 	    float ascent, descent;
+		fz_matrix tm = fz_identity;
 
 		measure_ascent_descent(doc, dr, da, text, &ascent, &descent);
 		fontsize = read_font_size_from_da(ctx, da);
 		if (fontsize)
 		{
-			fzbuf = create_text_buffer(ctx, &rect, da, -1.0, 2.0, 2.0 + fontsize * descent, text);
+			tm.e = 2.0;
+			tm.f = 2.0 + fontsize * descent;
+			fzbuf = create_text_buffer(ctx, &rect, da, -1.0, &tm, text);
 		}
 		else
 		{
-			fontsize = height;
-			fzbuf = create_text_buffer(ctx, &rect, da, fontsize, 2.0, 2.0 + height * descent, text);
+			fontsize = floor(height);
+			tm.e = 2.0;
+			tm.f = 2.0 + fontsize * descent;
+			fzbuf = create_text_buffer(ctx, &rect, da, fontsize, &tm, text);
 			tbox = measure_text(doc, dr, fzbuf);
 
 			if (tbox.x1 - tbox.x0 > width)
@@ -338,9 +344,10 @@ fz_buffer *create_text_appearance(pdf_document *doc, fz_rect *bbox, pdf_obj *dr,
 				/* Text doesn't fit. Regenerate with a calculated font size */
 				fz_drop_buffer(ctx, fzbuf);
 				fzbuf = NULL;
-				fontsize = height * width / (tbox.x1 - tbox.x0);
-				/* Use the same offset to keep the baseline constant */
-				fzbuf = create_text_buffer(ctx, &rect, da, fontsize, 2.0, 2.0 + height * descent, text);
+				/* Scale the text to fit but use the same offset
+				 * to keep the baseline constant */
+				tm.a = tm.d = width / (tbox.x1 - tbox.x0);
+				fzbuf = create_text_buffer(ctx, &rect, da, fontsize, &tm, text);
 			}
 		}
 	}